pfam10459, Peptidase_S46, Peptidase S46. Dipeptidyl-peptidase 7 (DPP-7) is the best characterized member of this family. It is a serine peptidase that is located on the cell surface and is predicted to have two N-terminal transmembrane domains.
TIGR01667, Uncharacterized_protein_HI_1680, integral membrane protein, YccS/YhfK family. This model represents two clades of putative transmembrane proteins including the E. coli YccS and YhfK proteins. The YccS hypothetical equivalog (TIGR01666) is found in beta and gamma proteobacteria, while the smaller YhfK group is only found in E. coli, Salmonella and Yersinia. TMHMM on the 19 hits to this model shows a consensus of 11 transmembrane helices separated into two clusters, an N-terminal cluster of 6 and a central cluster of 5. This would indicate two non-membrane domains one on each side of the membrane.
cd03673, Ap6A_hydrolase, Diadenosine hexaphosphate (Ap6A) hydrolase is a member of the Nudix hydrolase superfamily. Ap6A hydrolase specifically hydrolyzes diadenosine polyphosphates, but not ATP or diadenosine triphosphate, and it generates ATP as the product. Ap6A, the most preferred substrate, hydrolyzes to produce two ATP molecules, which is a novel hydrolysis mode for Ap6A. These results indicate that Ap6A hydrolase is a diadenosine polyphosphate hydrolase. It requires the presence of a divalent cation, such as Mn2+, Mg2+, Zn2+, and Co2+, for activity. Members of the Nudix superfamily are recognized by a highly conserved 23-residue nudix motif (GX5EX7REUXEEXGU, where U = I, L or V), which forms a structural motif that functions as a metal binding and catalytic site.
cd10449, GIY-YIG_SLX1_like, Catalytic GIY-YIG domain of yeast structure-specific endonuclease subunit SLX1 and its homologs. Structure-specific endonuclease subunit SLX1 is a highly conserved protein from yeast to human, with an N-terminal GIY-YIG endonuclease domain and a C-terminal PHD-type zinc finger postulated to mediate protein-protein or protein-DNA interaction. SLX1 forms active heterodimeric complexes with its SLX4 partner, which has additional roles in the DNA damage response that are distinct from the function of the heterodimeric SLX1-SLX4 nuclease. In yeast, the SLX1-SLX4 complex functions as a 5' flap endonuclease that maintains ribosomal DNA copy number, where SLX1 and SLX4 are shown to be catalytic and regulatory subunits, respectively. This endonuclease introduces single-strand cuts in duplex DNA on the 3' side of junctions with single-strand DNA. In addition to 5' flap endonuclease activity, human SLX1-SLX4 complex has been identified as a Holliday junction resolvase that promotes symmetrical cleavage of static and migrating Holliday junctions. SLX1 also associates with MUS81, EME1, C20orf94, PLK1, and ERCC1. Some eukaryotic SLX1 homologs lack the zinc finger domain, but possess intrinsically unstructured extensions of unknown function. These unstructured segments might be involved in interactions with other proteins.
TIGR01143, murF, UDP-N-acetylmuramoyl-tripeptide--D-alanyl-D-alanine ligase. This family consists of the strictly bacterial MurF gene of peptidoglycan biosynthesis. This enzyme is almost always UDP-N-acetylmuramoylalanyl-D-glutamyl-2,6-diaminopimelate--D-alanyl-D-alanyl ligase, but in a few species, MurE adds lysine rather than diaminopimelate. This enzyme acts on the product from MurE activity, and so is also subfamily rather than equivalog. Staphylococcus aureus is an example of species in this MurF protein would differ. [Cell envelope, Biosynthesis and degradation of murein sacculus and peptidoglycan].
cd02258, Peptidase_C25_N, Peptidase C25 family N-terminal domain, found in Arg-gingipain (Rgp), Lys-gingipain (Kgp) and related proteins. Peptidase family C25 is a unique class of cysteine proteases, exemplified by gingipain, which is produced by Porphyromonas gingivalis. P. gingivalis is one of the primary gram-negative pathogens that causes periodontitis, a disease that is also associated with other diseases such as diabetes and cardiovascular disease. Gingipains are a group of extracellular Arg- and Lys-specific proteinases called Arg-gingipain (Rgp) and Lys-gingipain (Kgp); RgpA and RgpB are homologous Arg-specific gingipains encoded by two closely related genes, rgpA and rgpB, while Lys-specific gingipain is encoded by the single kgp gene. Mutant studies have shown that, among the large quantities of proteolytic enzymes produced by P. gingivalis, these three proteases are major virulence factors of this bacterium. All three genes encode an N-terminal pre-pro fragment, followed by the protease domain; however, rgpA and kgp also encode additional C-terminal HA (hemaglutinin/adhesion) subunits which consist of several sequence-related adhesion domains. Although unique, their cysteine protease active site residues (His and Cys) forming the catalytic dyad are well-conserved, cleaving the C-terminal peptide bond with Arg or Lys residues. Gingipains are evolutionarily related to other highly specific proteases including caspases, clostripain, legumains, and separase. Gingipains function by dysregulating host defense and inflammatory responses, and degrading host proteins, e.g. tissue, cells, matrix, plasma and immunological proteins. They are proposed to enhance gingival crevicular fluid (GCF) production through activation of the kallikrein/kinin pathways, thus increasing vascular permeability and causing gingival inflammation, a distinctive feature of periodontitis. RgpA and RgpB are also able to cleave and activate coagulation factors IX and X in order to activate prothrombin to produce thrombin, which in turn increases production of GCF. The gingipains also play a pivotal role in the survival of P. gingivalis in the host by attacking the host defense system through cleavage of several immunological molecules, while at the same time evading the host-immune response by dysregulating the cytokine network.
cd10449, GIY-YIG_SLX1_like, Catalytic GIY-YIG domain of yeast structure-specific endonuclease subunit SLX1 and its homologs. Structure-specific endonuclease subunit SLX1 is a highly conserved protein from yeast to human, with an N-terminal GIY-YIG endonuclease domain and a C-terminal PHD-type zinc finger postulated to mediate protein-protein or protein-DNA interaction. SLX1 forms active heterodimeric complexes with its SLX4 partner, which has additional roles in the DNA damage response that are distinct from the function of the heterodimeric SLX1-SLX4 nuclease. In yeast, the SLX1-SLX4 complex functions as a 5' flap endonuclease that maintains ribosomal DNA copy number, where SLX1 and SLX4 are shown to be catalytic and regulatory subunits, respectively. This endonuclease introduces single-strand cuts in duplex DNA on the 3' side of junctions with single-strand DNA. In addition to 5' flap endonuclease activity, human SLX1-SLX4 complex has been identified as a Holliday junction resolvase that promotes symmetrical cleavage of static and migrating Holliday junctions. SLX1 also associates with MUS81, EME1, C20orf94, PLK1, and ERCC1. Some eukaryotic SLX1 homologs lack the zinc finger domain, but possess intrinsically unstructured extensions of unknown function. These unstructured segments might be involved in interactions with other proteins.
TIGR03524, gliding_motility_protein_GldJ, gliding motility-associated lipoprotein GldJ. Members of this protein family are exclusive to the Bacteroidetes phylum (previously Cytophaga-Flavobacteria-Bacteroides). GldJ is a lipoprotein linked to a type of rapid surface gliding motility found in certain Bacteroidetes, such as Flavobacterium johnsoniae. Knockouts of GldJ abolish the gliding phenotype. GldJ is homologous to GldK. There is a GldJ homolog in Cytophaga hutchinsonii and several other species that has a different, shorter architecture and is represented by a separate model. Gliding motility appears closely linked to chitin utilization in the model species Flavobacterium johnsoniae. Bacteroidetes with members of this protein family appear to have all of the genes associated with gliding motility.
TIGR03522, GldA_ABC_ATP, gliding motility-associated ABC transporter ATP-binding subunit GldA. Members of this protein family are exclusive to the Bacteroidetes phylum (previously Cytophaga-Flavobacteria-Bacteroides). GldA is an ABC transporter ATP-binding protein (pfam00005) linked to a type of rapid surface gliding motility found in certain Bacteroidetes, such as Flavobacterium johnsoniae and Cytophaga hutchinsonii. Knockouts of GldA abolish the gliding phenotype. Gliding motility appears closely linked to chitin utilization in the model species Flavobacterium johnsoniae. Bacteroidetes with members of this protein family appear to have all of the genes associated with gliding motility.
pfam09995, DUF2236, Uncharacterized protein conserved in bacteria (DUF2236). This domain, found in various hypothetical bacterial proteins, has no known function. This family contains a highly conserved arginine and histidine that may be active site residues for an as yet unknown catalytic activity.
cd01347, ligand_gated_channel, TonB dependent/Ligand-Gated channels are created by a monomeric 22 strand (22,24) anti-parallel beta-barrel. Ligands apparently bind to the large extracellular loops. The N-terminal 150-200 residues form a plug from the periplasmic end of barrel. Energy (proton-motive force) and TonB-dependent conformational alteration of channel (parts of plug, and loops 7 and 8) allow passage of ligand. FepA residues 12-18 form the TonB box, which mediates the interaction with the TonB-containing inner membrane complex. TonB preferentially interacts with ligand-bound receptors. Transport thru the channel may resemble passage thru an air lock. In this model, ligand binding leads to closure of the extracellular end of pore, then a TonB-mediated signal facillitates opening of the interior side of pore, deforming the N-terminal plug and allowing passage of the ligand to the periplasm. Such a mechanism would prevent the free diffusion of small molecules thru the pore.
pfam01242, PTPS, 6-pyruvoyl tetrahydropterin synthase. 6-Pyruvoyl tetrahydrobiopterin synthase catalyzes the conversion of dihydroneopterin triphosphate to 6-pyruvoyl tetrahydropterin, the second of three enzymatic steps in the synthesis of tetrahydrobiopterin from GTP. The functional enzyme is a hexamer of identical subunits.
cd07398, MPP_YbbF-LpxH, Escherichia coli YbbF/LpxH and related proteins, metallophosphatase domain. YbbF/LpxH is an Escherichia coli UDP-2,3-diacylglucosamine hydrolase thought to catalyze the fourth step of lipid A biosynthesis, in which a precursor UDP-2,3-diacylglucosamine is hydrolyzed to yield 2,3-diacylglucosamine 1-phosphate and UMP. YbbF belongs to the metallophosphatase (MPP) superfamily. MPPs are functionally diverse, but all share a conserved domain with an active site consisting of two metal ions (usually manganese, iron, or zinc) coordinated with octahedral geometry by a cage of histidine, aspartate, and asparagine residues. The MPP superfamily includes: Mre11/SbcD-like exonucleases, Dbr1-like RNA lariat debranching enzymes, YfcE-like phosphodiesterases, purple acid phosphatases (PAPs), YbbF-like UDP-2,3-diacylglucosamine hydrolases, and acid sphingomyelinases (ASMases). The conserved domain is a double beta-sheet sandwich with a di-metal active site made up of residues located at the C-terminal side of the sheets. This domain is thought to allow for productive metal coordination.
COG0513, SrmB, Superfamily II DNA and RNA helicases [DNA replication, recombination, and repair / Transcription / Translation, ribosomal structure and biogenesis].
cd00093, HTH_XRE, Helix-turn-helix XRE-family like proteins. Prokaryotic DNA binding proteins belonging to the xenobiotic response element family of transcriptional regulators.
cd11350, AmyAc_4, Alpha amylase catalytic domain found in an uncharacterized protein family. The Alpha-amylase family comprises the largest family of glycoside hydrolases (GH), with the majority of enzymes acting on starch, glycogen, and related oligo- and polysaccharides. These proteins catalyze the transformation of alpha-1,4 and alpha-1,6 glucosidic linkages with retention of the anomeric center. The protein is described as having 3 domains: A, B, C. A is a (beta/alpha) 8-barrel; B is a loop between the beta 3 strand and alpha 3 helix of A; C is the C-terminal extension characterized by a Greek key. The majority of the enzymes have an active site cleft found between domains A and B where a triad of catalytic residues (Asp, Glu and Asp) performs catalysis. Other members of this family have lost the catalytic activity as in the case of the human 4F2hc, or only have 2 residues that serve as the catalytic nucleophile and the acid/base, such as Thermus A4 beta-galactosidase with 2 Glu residues (GH42) and human alpha-galactosidase with 2 Asp (GH31). The family members are quite extensive and include: alpha amylase, maltosyltransferase, cyclodextrin glycotransferase, maltogenic amylase, neopullulanase, isoamylase, 1,4-alpha-D-glucan maltotetrahydrolase, 4-alpha-glucotransferase, oligo-1,6-glucosidase, amylosucrase, sucrose phosphorylase, and amylomaltase.
pfam14014, DUF4230, Protein of unknown function (DUF4230). This family of proteins is functionally uncharacterized. This family of proteins is found in bacteria. Proteins in this family are typically between 203 and 228 amino acids in length.
pfam02617, ClpS, ATP-dependent Clp protease adaptor protein ClpS. In the bacterial cytosol, ATP-dependent protein degradation is performed by several different chaperone-protease pairs, including ClpAP. ClpS directly influences the ClpAP machine by binding to the N-terminal domain of the chaperone ClpA. The degradation of ClpAP substrates, both SsrA-tagged proteins and ClpA itself, is specifically inhibited by ClpS. ClpS modifies ClpA substrate specificity, potentially redirecting degradation by ClpAP toward aggregated proteins.
pfam00213, OSCP, ATP synthase delta (OSCP) subunit. The ATP D subunit from E. coli is the same as the OSCP subunit which is this family. The ATP D subunit from metazoa are found in family pfam00401.
cd18121, ATP-synt_Fo_c, membrane-bound Fo complex of F-ATP synthase, subunit c. Subunit c (also called subunit 9, or proteolipid) of the Fo complex of F-ATP synthase. The F-ATP synthase (also called FoF1-ATPase) consists of two structural domains: the F1 (factor one) complex containing the soluble catalytic core, and the Fo (oligomycin sensitive factor) complex containing the membrane proton channel, linked together by a central stalk and a peripheral stalk. F1 is composed of alpha, beta, gamma, delta, and epsilon subunits with a stoichiometry of 3:3:1:1:1, while Fo consists of the three subunits a, b, and c (1:2:10-14). An oligomeric ring of 10-14 c subunits (c-ring) make up the Fo rotor. The flux of protons though the ATPase channel (Fo) drives the rotation of the c-ring, which in turn is coupled to the rotation of the F1 complex gamma subunit rotor due to the permanent binding between the gamma and epsilon subunits of F1 and the c-ring of Fo. The F-ATP synthases are primarily found in the inner membranes of eukaryotic mitochondria, in the thylakoid membranes of chloroplasts, or in the plasma membranes of bacteria. The F-ATP synthases are the primary producers of ATP, using the proton gradient generated by oxidative phosphorylation (mitochondria) or photosynthesis (chloroplasts). Alternatively, under conditions of low driving force, ATP synthases function as ATPases, thus generating a transmembrane proton or Na(+) gradient at the expense of energy derived from ATP hydrolysis. This group also includes F-ATP synthase that has also been found in the archaea Methanosarcina acetivorans.
cd03809, GT4_MtfB-like, glycosyltransferases MtfB, WbpX, and similar proteins. This family is most closely related to the GT4 family of glycosyltransferases. MtfB (mannosyltransferase B) in E. coli has been shown to direct the growth of the O9-specific polysaccharide chain. It transfers two mannoses into the position 3 of the previously synthesized polysaccharide.
