TIGR01903, Hypothetical_protein., CRISPR type III-A/MTUBE-associated RAMP protein Csm4. CRISPR is a term for Clustered Regularly Interspaced Short Palidromic Repeats. A number of protein families appear only in association with these repeats and are designated Cas (CRISPR associated) proteins. Members of this cas gene family are found in the mtube subtype of CRISPR/cas locus and designated Csm4, for CRISPR/cas Subtype Mtube, protein 4.
TIGR02985, Sig70_bacteroi1, RNA polymerase sigma-70 factor, Bacteroides expansion family 1. This group of sigma factors are members of the sigma-70 family (TIGR02937) and are found primarily in the genus Bacteroides. This family appears to have resulted from a lineage-specific expansion as B. thetaiotaomicron VPI-5482, Bacteroides forsythus ATCC 43037, Bacteroides fragilis YCH46 and Bacteroides fragilis NCTC 9343 contain 25, 12, 24 and 23 members, respectively. There are currentlyonly two known members of this family outside of the Bacteroides, in Rhodopseudomonas and Bradyrhizobium.
cd09725, Cas2_I_II_III, CRISPR/Cas system-associated protein Cas2. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Cas2 is present in majority of CRISPR/Cas systems along with Cas1; RNAse specific to U-rich regions; Possesses an RRM/ferredoxin fold.
TIGR01899, cas_TM1807_csm5, CRISPR type III-A/MTUBE-associated RAMP protein Csm5. CRISPR is a term for Clustered Regularly Interspaced Short Palidromic Repeats. A number of protein families appear only in association with these repeats and are designated Cas (CRISPR associated) proteins. Members of this cas gene family are found in the mtube subtype of CRISPR/cas locus and designated Csm5, for CRISPR/cas Subtype Mtube, protein 5.
TIGR01877, CRISPR-associated_endoribonuclease_Cas6_1, CRISPR-associated endoribonuclease Cas6. CRISPR is a term for Clustered, Regularly Interspaced Short Palidromic Repeats. A number of protein families appear only in association with these repeats and are designated Cas (CRISPR-Associated) proteins. This broadly distributed, highly divergent Cas family is now characterized as an endoribonuclease that generates guide RNAs for host defense against phage and other invaders. The family contains a C-terminal motif GXGXXXXXGXG, where the each X between two Gly is hydrophobic and the spacer XXXXX contains (usually) one Arg or Lys. The seed alignment for the current version of this model has gappy columns removed. Members of this protein family are found associated with several different CRISPR/cas system subtypes, and consequently we designate this family Cas6.
cd09747, Csx1_III-U, CRISPR/Cas system-associated protein Csx1. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Protein of this family often fused to HTH domain; Some proteins could have an additional fusion with RecB-family nuclease domain; Core domain appears to have a Rossmann-like fold; loosely associated with CRISPR/Cas systems; also known as Cas02710 family.
cd09725, Cas2_I_II_III, CRISPR/Cas system-associated protein Cas2. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Cas2 is present in majority of CRISPR/Cas systems along with Cas1; RNAse specific to U-rich regions; Possesses an RRM/ferredoxin fold.
TIGR02937, RNA_polymerase_sigma_factor, RNA polymerase sigma factor, sigma-70 family. This model encompasses all varieties of the sigma-70 type sigma factors including the ECF subfamily. A number of sigma factors have names with a different number than 70 (i.e. sigma-38), but in fact, all except for the Sigma-54 family (TIGR02395) are included within this family. Several Pfam models hit segments of these sequences including Sigma-70 region 2 (pfam04542) and Sigma-70, region 4 (pfam04545), but not always above their respective trusted cutoffs.
TIGR01899, cas_TM1807_csm5, CRISPR type III-A/MTUBE-associated RAMP protein Csm5. CRISPR is a term for Clustered Regularly Interspaced Short Palidromic Repeats. A number of protein families appear only in association with these repeats and are designated Cas (CRISPR associated) proteins. Members of this cas gene family are found in the mtube subtype of CRISPR/cas locus and designated Csm5, for CRISPR/cas Subtype Mtube, protein 5.
cd09679, Cas10_III, CRISPR/Cas system-associated protein Cas10. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Multidomain protein with permuted HD nuclease domain, palm domain and Zn-ribbon; MTH326-like has inactivated polymerase catalytic domain; alr1562 and slr7011 - predicted only on the basis of size, presence of HD domain, and location with RAMPs in one operon; signature gene for type III; also known as Crm2 family.
pfam18145, SAVED, SMODS-associated and fused to various effectors sensor domain. Predicted to function as a sensor domain, sensing nucleotides or nucleotide derivatives generated by SMODS and other nucleotide synthetase domains. The sensing of ligands by SAVED is predicted to activate effectors deployed by a class of conflict systems which are reliant on the on the production and sensing of the nucleotide second messengers.
pfam03750, Csm2_III-A, Csm2 Type III-A. Clusters of short DNA repeats with non-homologous spacers, which are found at regular intervals in the genomes of phylogenetically distinct prokaryotic species, comprise a family with recognisable features. This family is known as CRISPR (short for Clustered Regularly Interspaced Short Palindromic Repeats). A number of protein families appear only in association with these repeats and are designated Cas (CRISPR-associated) proteins. This entry represents Csm2 Type III-A, a family of Cas proteins also known as TM1810/Csm2.
cd09680, Cas10_III, CRISPR/Cas system-associated protein Cas10. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Multidomain protein with permuted HD nuclease domain, palm domain and Zn-ribbon; signature gene for type III; also known as Csm1 family.
cd09728, Csx1_III-U, CRISPR/Cas system-associated protein Csx1. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Protein of this family often fused to HTH domain; Some proteins could have an additional fusion with RecB-family nuclease domain; Core domain appears to have a Rossmann-like fold; loosely associated with CRISPR/Cas systems; also known as DxTHG family.
TIGR01903, Hypothetical_protein., CRISPR type III-A/MTUBE-associated RAMP protein Csm4. CRISPR is a term for Clustered Regularly Interspaced Short Palidromic Repeats. A number of protein families appear only in association with these repeats and are designated Cas (CRISPR associated) proteins. Members of this cas gene family are found in the mtube subtype of CRISPR/cas locus and designated Csm4, for CRISPR/cas Subtype Mtube, protein 4.
TIGR02580, putative_CRISPR-associated_protein, CRISPR type III-B/RAMP module RAMP protein Cmr4. This model represents a CRISPR-associated protein from the family that includes TM1792 of Thermotoga maritima. This family is part of the broad RAMP superfamily (pfam03787) collection of CRISPR-associated proteins. It is the fourth of a recurring set of six proteins, four of are in the RAMP superfamily, that we designate the CRISPR RAMP module.
pfam09701, Cas_Cmr5, CRISPR-associated protein (Cas_Cmr5). CRISPR is a term for Clustered, Regularly Interspaced Short Palindromic Repeats. A number of protein families appear only in association with these repeats and are designated Cas (CRISPR-Associated) proteins. This family, represented by TM1791.1 of Thermotoga maritima, is found in both archaeal and bacterial species.
cd09722, Cas1_I-B, CRISPR/Cas system-associated protein Cas1. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Cas1 is the most universal CRISPR system protein thought to be involved in spacer integration; Cas1 is metal-dependent deoxyribonuclease, also binds RNA; Shown to possess a unique fold consisting of a N-terminal beta-strand domain and a C-terminal alpha-helical domain.
TIGR01877, CRISPR-associated_endoribonuclease_Cas6_1, CRISPR-associated endoribonuclease Cas6. CRISPR is a term for Clustered, Regularly Interspaced Short Palidromic Repeats. A number of protein families appear only in association with these repeats and are designated Cas (CRISPR-Associated) proteins. This broadly distributed, highly divergent Cas family is now characterized as an endoribonuclease that generates guide RNAs for host defense against phage and other invaders. The family contains a C-terminal motif GXGXXXXXGXG, where the each X between two Gly is hydrophobic and the spacer XXXXX contains (usually) one Arg or Lys. The seed alignment for the current version of this model has gappy columns removed. Members of this protein family are found associated with several different CRISPR/cas system subtypes, and consequently we designate this family Cas6.
cd09684, Csm3_III-A, CRISPR/Cas system-associated RAMP superfamily protein Csm3. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; RAMP superfamily protein.
cd09661, Cmr6_III-B, CRISPR/Cas system-associated RAMP superfamily protein Cmr6. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; RAMP superfamily protein; This protein is a subunit of Cmr complex.
cd09725, Cas2_I_II_III, CRISPR/Cas system-associated protein Cas2. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Cas2 is present in majority of CRISPR/Cas systems along with Cas1; RNAse specific to U-rich regions; Possesses an RRM/ferredoxin fold.
TIGR03641, cas1_HMARI, CRISPR-associated endonuclease Cas1, subtype I-B/HMARI/TNEAP. The CRISPR-associated protein Cas1 is virtually universal to CRISPR systems. CRISPR, an acronym for Clustered Regularly Interspaced Short Palindromic Repeats, is prokaryotic immunity system for foreign DNA, mostly from phage. CRISPR systems belong to different subtypes, distinguished by both nature of the repeats, the makeup of the cohort of associated Cas proteins, and by molecular phylogeny within the more universal Cas proteins such as this one. This model is of type EXCEPTION and provides more specific information than the EQUIVALOG model TIGR00287. It describes Cas1 subgroup that includes Cas1 proteins of the related HMARI and TNEAP subtypes of CRISPR/Cas system.
cd09730, Cas8a1_I-A, CRISPR/Cas system-associated protein Cas8a1. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Large proteins, some contain Zn-finger domain; signature gene for I-A subtype; also known as TM1802 family.
pfam09986, DUF2225, Uncharacterized protein conserved in bacteria (DUF2225). This domain, found in various hypothetical bacterial proteins, has no known function.
cd09725, Cas2_I_II_III, CRISPR/Cas system-associated protein Cas2. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Cas2 is present in majority of CRISPR/Cas systems along with Cas1; RNAse specific to U-rich regions; Possesses an RRM/ferredoxin fold.
cd01949, GGDEF, Diguanylate-cyclase (DGC) or GGDEF domain. Diguanylate-cyclase (DGC) or GGDEF domain: Originally named after a conserved residue pattern, and initially described as a domain of unknown function 1 (DUF1). This domain is widely present in bacteria, linked to a wide range of non-homologous domains in a variety of cell signaling proteins. The domain shows homology to the adenylyl cyclase catalytic domain. This correlates with the functional information available on two GGDEF-containing proteins, namely diguanylate cyclase and phosphodiesterase A of Acetobacter xylinum, both of which regulate the turnover of cyclic diguanosine monophosphate. Together with the EAL domain, GGDEF might be involved in regulating cell surface adhesion in bacteria.
pfam03961, FapA, Flagellar Assembly Protein A. Members of this family include FapA (flagellar assembly protein A), found in Vibrio vulnificus. The synthesis of flagella allows bacteria to respond to chemotaxis by facilitating motility. Studies examining the role of FapA show that the loss or delocalization of FapA results in a complete failure of the flagellar biosynthesis and motility in response to glucose mediated chemotaxis. The polar localization of FapA is required for flagellar synthesis, and dephosphorylated EIIAGlc (Glucose-permease IIA component) inhibited the polar localization of FapA through direct interaction.
pfam01894, UPF0047, Uncharacterized protein family UPF0047. This family has no known function. The alignment contains a conserved aspartate and histidine that may be functionally important.
TIGR01215, Cell_division_topological_specificity_factor, cell division topological specificity factor MinE. This protein is involved in the process of cell division. This protein prevents the proteins MinC and MinD to inhibit cell division at internal sites, but allows inhibiton at polar sites. This allows for correct cell division at the proper sites. [Cellular processes, Cell division].
cd14486, 3D_domain, 3D domain, named for 3 conserved aspartate residues, is found in mltA-like lytic transglycosylases and numerous other contexts. This family contains the 3D domain, named for its 3 conserved aspartates. It is found in conjunction with numerous other domains such as MltA (membrane-bound lytic murein transglycosylase A). These aspartates are critical active site residues of mltA-like lytic transglycosylases. Escherichia coli peptidoglycan lytic transglycosylase (LT) initiates cell wall recycling in response to damage, during bacterial fission, and cleaves peptidoglycan (PG) to create functional spaces in its wall. MltA has 2 domains, separated by a large groove, where the peptidoglycan strand binds. The C-terminus has a double-psi beta barrel fold within the 3D domain, which forms the larger A domain along with the N-terminal region of Mlts, but is also found in various other domain architectures. Peptigoglycan (also known as murein) chains, the primary structural component of bacterial cells walls, are comprised of alternating beta-1-4-linked N-acetylmuramic acid (MurNAc) and N-acetyl-D-glucosamine (GlcNAc); lytic transglycosylases (LTs) cleave this beta-1-4 bond. Typically, LTs are exolytic, releasing Metabolite 1 (GlcNAc-anhMurNAc-L-Ala-D-Glu-m-Dap-D-Ala-D-Ala) from the ends of the PG strands. In contrast, membrane-bound lytic murein transglycosylase E (MltE) is endolytic , cleaving in the middle of PG strands, with further processing to Metabolite 1 accomplished by other LTs. In E. coli, there are six membrane- bound LTs: MltA-MltF and soluble Slt70. Slt35 is a soluble fragment cleaved from MltB. Bacterial LTs are classified in 4 families: Family 1 includes slt70 MltC-MltF, Family 2 includes MltA, Family 3 includes MltB, and family 4 of bacteriophage origin. While most LTs are related members of the lysozyme-like lytic transglycosylase family, MltA represents a distinct fold and sequence conservation.
TIGR02592, hypothetical_protein_CTC_01466, CRISPR-associated protein Cas5, subtype I-B/HMARI. This is a CRISPR-associated protein unique to the hmari subtype of cas genes and CRISPR repeat, which is the only subtype present in Haloarcula marismortui ATCC 43049. The hmari type, though uncommon, is also found in the Aquificae, Thermotogae, Firmicutes, and Dictyoglomi.
pfam01930, Cas_Cas4, Domain of unknown function DUF83. This domain has no known function. The domain contains three conserved cysteines at its C-terminus.
TIGR02590, hypothetical_protein_MM_0563, CRISPR-associated protein Cas7/Csh2, subtype I-B/HMARI. This model represents one of two closely related CRISPR-associated proteins that belong to the larger family of TIGR01595. Members are the Csh2 protein of the Hmari subtype of CRISPR/cas system. CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. The related model is TIGR02589, the Csd3 protein of the Dvulg CRISPR subtype.
pfam03706, LPG_synthase_TM, Lysylphosphatidylglycerol synthase TM region. LPG_synthase_TM is the N-terminal region of this family of bacterial phosphatidylglycerol lysyltransferases. The function of the family is to add lysyl groups to membrane lipids, and this region is the transmembrane domain of 7xTMs. In order to counteract attack by membrane-damaging external cationic antimicrobial molecules - from host immune systems, bacteriocins, defencins, etc - bacteria modify their anionic membrane phosphatidylglycerol with positively-charged L-lysine; this results in repulsion of the foreign cationic peptides.
cd00622, PLPDE_III_ODC, Type III Pyridoxal 5-phosphate (PLP)-Dependent Enzyme Ornithine Decarboxylase. This subfamily is composed mainly of eukaryotic ornithine decarboxylases (ODC, EC 4.1.1.17) and ODC-like enzymes from prokaryotes represented by Vibrio vulnificus LysineOrnithine decarboxylase. These are fold type III PLP-dependent enzymes that differ from most bacterial ODCs which are fold type I PLP-dependent enzymes. ODC participates in the formation of putrescine by catalyzing the decarboxylation of ornithine, the first step in polyamine biosynthesis. Members of this subfamily contain an N-terminal PLP-binding TIM-barrel domain and a C-terminal beta-sandwich domain, similar to bacterial alanine racemases. They exist as homodimers with active sites that lie at the interface between the TIM barrel domain of one subunit and the beta-sandwich domain of the other subunit. Homodimer formation and the presence of the PLP cofactor are required for catalytic activity. Also members of this subfamily are proteins with homology to ODC but do not possess any catalytic activity, the Antizyme inhibitor (AZI) and ODC-paralogue (ODC-p). AZI binds to the regulatory protein Antizyme with a higher affinity than ODC and prevents ODC degradation. ODC-p is a novel ODC-like protein, present only in mammals, that is specifically exressed in the brain and testes. ODC-p may function as a tissue-specific antizyme inhibitory protein.
cd09754, Cas8a1_I-A, CRISPR/Cas system-associated protein Cas8a1. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Large proteins, some contain Zn-finger domain; signature gene for I-A subtype; also known as CXXC_CXXC family.
pfam01905, DevR, CRISPR-associated negative auto-regulator DevR/Csa2. This group of families is one of several protein families that are always found associated with prokaryotic CRISPRs, themselves a family of clustered regularly interspaced short palindromic repeats, DNA repeats found in nearly half of all bacterial and archaeal genomes. These DNA repeat regions have a remarkably regular structure: unique sequences of constant size, called spacers, sit between each pair of repeats. It has been shown that the CRISPRs are virus-derived sequences acquired by the host to enable them to resist viral infection. The Cas proteins from the host use the CRISPRs to mediate an antiviral response. After transcription of the CRISPR, a complex of Cas proteins termed Cascade cleaves a CRISPR RNA precursor in each repeat and retains the cleavage products containing the virus-derived sequence. Assisted by the helicase Cas3, these mature CRISPR RNAs then serve as small guide RNAs that enable Cascade to interfere with virus proliferation. Cas5 contains an endonuclease motif, whose inactivation leads to loss of resistance, even in the presence of phage-derived spacers. This family used to be known as DUF73. DevR appears to be negative auto-regulator within the system.
TIGR03641, cas1_HMARI, CRISPR-associated endonuclease Cas1, subtype I-B/HMARI/TNEAP. The CRISPR-associated protein Cas1 is virtually universal to CRISPR systems. CRISPR, an acronym for Clustered Regularly Interspaced Short Palindromic Repeats, is prokaryotic immunity system for foreign DNA, mostly from phage. CRISPR systems belong to different subtypes, distinguished by both nature of the repeats, the makeup of the cohort of associated Cas proteins, and by molecular phylogeny within the more universal Cas proteins such as this one. This model is of type EXCEPTION and provides more specific information than the EQUIVALOG model TIGR00287. It describes Cas1 subgroup that includes Cas1 proteins of the related HMARI and TNEAP subtypes of CRISPR/Cas system.
TIGR01372, sarcosine_oxidase_alpha_subunit, sarcosine oxidase, alpha subunit family, heterotetrameric form. This model describes the alpha subunit of a family of known and putative heterotetrameric sarcosine oxidases. Five operons of such oxidases are found in Mesorhizobium loti and three in Agrobacterium tumefaciens, a high enough copy number to suggest that not all members are share the same function. The model is designated as subfamily rather than equivalog for this reason.Sarcosine oxidase catalyzes the oxidative demethylation of sarcosine to glycine. The reaction converts tetrahydrofolate to 5,10-methylene-tetrahydrofolate. The enzyme is known in monomeric and heterotetrameric (alpha,beta,gamma,delta) forms [Energy metabolism, Amino acids and amines].
cd09725, Cas2_I_II_III, CRISPR/Cas system-associated protein Cas2. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Cas2 is present in majority of CRISPR/Cas systems along with Cas1; RNAse specific to U-rich regions; Possesses an RRM/ferredoxin fold.
cd07779, FGGY_ygcE_like, uncharacterized ygcE-like proteins. This subfamily consists of uncharacterized hypothetical bacterial proteins with similarity to Escherichia coli sugar kinase ygcE , whose functional roles are not yet clear. Escherichia coli ygcE is recognized by this model, but is not present in the alignment as it contains a deletion relative to other members of the group. These proteins belong to the FGGY family of carbohydrate kinases, the monomers of which contain two large domains, which are separated by a deep cleft that forms the active site. This model includes both the N-terminal domain, which adopts a ribonuclease H-like fold, and the structurally related C-terminal domain.
TIGR01587, CRISPR-associated_endonuclease/helicase_Cas3, CRISPR-associated helicase Cas3. This model represents the highly conserved core region of an alignment of Cas3, a protein found in association with CRISPR repeat elements in a broad range of bacteria and archaea. Cas3 appears to be a helicase, with regions found by pfam00270 (DEAD/DEAH box helicase) and pfam00271 (Helicase conserved C-terminal domain). Some but not all members have an N-terminal HD domain region (pfam01966) that is not included within this model.
TIGR01895, conserved_hypothetical_protein, CRISPR-associated protein Cas5, subtype I-B/TNEAP. CRISPR is a term for Clustered Regularly Interspaced Short Palidromic Repeats. A number of protein families appear only in association with these repeats and are designated Cas (CRISPR associated) proteins. This family is represented by TM1800 from Thermotoga maritima. It is related to TIGR01868 (CRISPR-associated protein, CT1976 family).
cd09652, Cas6-I-III, CRISPR/Cas system-associated RAMP superfamily protein Cas6. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Cas6 is an endoribonuclease that generates crRNAs, predicted subunit of Cascade complex; RAMP superfamily protein; Possesses double RRM/ferredoxin fold.
pfam06283, ThuA, Trehalose utilisation. This family consists of several bacterial ThuA like proteins. ThuA appears to be involved in utilisation of trehalose. The thuA and thuB genes form part of the trehalose/sucrose transport operon thuEFGKAB, which is located on the pSymB megaplasmid. The thuA and thuB genes are induced in vitro by trehalose but not by sucrose and the extent of its induction depends on the concentration of trehalose available in the medium.
pfam01930, Cas_Cas4, Domain of unknown function DUF83. This domain has no known function. The domain contains three conserved cysteines at its C-terminus.
cd17517, RMtype1_S_EcoKI_StySPI-TRD2-CR2_like, Type I restriction-modification system specificity (S) subunit Target Recognition Domain-ConseRved domain (TRD-CR),similar to Escherichia coli str. K-12 substr. MG1655 S subunit (S.EcoKI) TRD2-CR2, Salmonella enterica subsp. enterica serovar Potsdam S subunit (S.StySPI) TRD2-CR2, and other TRD-CR's. Escherichia coli str. K-12 substr. MG1655 S subunit (S.EcoKI) recognizes 5'... AACNNNNNNGTGC ... 3' and Salmonella enterica subsp. enterica serovar Potsdam S subunit (S.StySPI) recognizes 5'... AACNNNNNNGTRC ... 3'. The restriction-modification (RM) system S subunit consists of two variable target recognition domains (TRD1 and 2) and two conserved regions (CR1 and CR2) which separate the TRDs. The TRDs each bind to different specific sequences in the DNA. For example, S.EcoKI-TRD1 and S.StySPI-TRD1 both recognize AAC/GTT, S.EcoKI-TRD2 recognizes GCAC/GTGC and S.StySPI-TRD2 recognizes GYAC/GTRC. RM systems protect a bacterial cell against invasion of foreign DNA by endonucleolytic cleavage of DNA that lacks a site specific modification. The host genome is protected from cleavage by methylation of specific nucleotides in the target sites. In type I systems, both restriction and modification activities are present in one enzyme complex composed of one DNA specificity (S) subunit (this family), two modification (M) subunits and two restriction (R) subunits. This model contains both TRD1-CR1 and TRD2-CR2.It also includes TRD-CR-like sequence-recognition domains of various type II restriction enzymes and methyltransferases, such as Pseudomonas putida Jo 4-731 Type IIG restriction enzyme/N6-adenine DNA methyltransferase (RM.PpiI), and type I DNA methyltransferases such as Bacillus cereus BDRD-ST24 M subunit of Type I N6-adenine DNA methyltransferase (M.Bce24ORF51270P). RM.PpiI recognizes 5' ... GAACNNNNNCTC ... 3'.
