TIGR04226, Fimbrial_subunit_type_2, fimbrial isopeptide formation D2 domain. The Streptococcus Pneumoniae pilus backbone protein, RrgB, has three tandem domains with Lys-to-Asn isopeptide bonds, but these three regions are extremely divergent in sequence. This model represents the homology domain family of the D2 domain. It occurs just once in many surface proteins but up to twenty times in some pilin subunit proteins. Three of every four members have the typical Gram-positive C-terminal motif, LPXTG, although in many cases this motif may be involved in pilin subunit cross-linking rather than cell wall attachment. Proteins with this domain include fimbrial proteins with lectin-like adhesion functions, and the majority of characterized members are involved in surface adhesion to host structures.
pfam13399, LytR_C, LytR cell envelope-related transcriptional attenuator. This family appears at the C-terminus of members of the LytR_cpsA_psr, pfam03816, family.
pfam13224, DUF4032, Domain of unknown function (DUF4032). This presumed domain is functionally uncharacterized. This domain family is found in bacteria, and is approximately 170 amino acids in length. The family is found in association with pfam06293.
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.
TIGR02692, putative_tRNA_nucleotidyltransferase, tRNA adenylyltransferase. The enzyme tRNA adenylyltransferase, also called tRNA-nucleotidyltransferase and CCA-adding enzyme, can add or repair the required CCA triplet at the 3'-end of tRNA molecules. Genes encoding tRNA include the CCA tail in some but not all bacteria, and this enzyme may be required for viability. Members of this family represent a distinct clade within the larger family pfam01743 (tRNA nucleotidyltransferase/poly(A) polymerase family protein). The example from Streptomyces coelicolor was shown to act as a CCA-adding enzyme and not as a poly(A) polymerase. [Protein synthesis, tRNA and rRNA base modification].
cd05827, Sortase_C, Sortase domain found in class C sortases. Class C sortases are membrane-bound cysteine transpeptidases broadly distributed in Gram-positive bacteria (mainly present in Firmicutes and Actinobacteria). They function as pilin polymerases responsible for the assembly of pili, which are multi-subunit hair-like fibres that extend from the cell surface to promote microbial adhesion and biofilm formation. First, one or more class C sortases form the long thin shaft of the pilus through linking together pilin subunits via isopeptide bonds. The base of the pilus is then anchored to the cell wall by a housekeeping sortase or, in some cases, the class C sortase itself. Depending upon the organism both the number and type of sortase enzymes involved varies, and in some cases, accessory factors appear to be needed. In three-component spaA pilus from Corynebacterium diphtheriae, the prototypical class C sortase (named Cd-SrtA) catalyzes polymerization of the SpaA-type pilus, consisting of the shaft pilin SpaA, tip pilin SpaC and minor pilin SpaB. The pilus shaft is then attached to the cell wall by a housekeeping class E sortase, Cd-SrtF. In the absence of Cd-SrtF, Cd-SrtA attaches the pilus to the cell wall, albeit at a reduced rate. Cd-SrtA can recognize two distinct sorting signals (LPLTG in SpaA and SpaC, and LAFTG in SpaB) and it can employ lysine residues that originate from different proteins (either Lys190 within the pilin motif of SpaA or Lys139 in SpaB). However, Cd-SrtA cannot be able to polymerize the major pilin subunit SpaH, even though it contains LPLTG motif. In two-component pili of prototypical Bacillus cereus, the class C sortase (named Bc-SrtD) cleaves related sorting signals within a major pilin protein BcpA (LPVTG) and a minor tip pilin BcpB (IPNTG), and catalyzes a transpeptidation that joins the threonine residues in each signal to the side-chain of Lys162 in BcpA (located within a pilin motif). Unlike the SpaA pilus in C. diphtheriae, in B. cereus Bc-SrtD is unable to covalently attach the pilus to the cell wall without the help of the housekeeping sortase.
pfam17802, SpaA, Prealbumin-like fold domain. This entry contains a prealbumin-like domain from a wide variety of bacterial surface proteins. This entry corresponds to domain 1 and domain 3 of SpaA from Corynebacterium diphtheriae. Some members of this family contain an isopeptide bond.
cd14014, STKc_PknB_like, Catalytic domain of bacterial Serine/Threonine kinases, PknB and similar proteins. STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. This subfamily includes many bacterial eukaryotic-type STKs including Staphylococcus aureus PknB (also called PrkC or Stk1), Bacillus subtilis PrkC, and Mycobacterium tuberculosis Pkn proteins (PknB, PknD, PknE, PknF, PknL, and PknH), among others. S. aureus PknB is the only eukaryotic-type STK present in this species, although many microorganisms encode for several such proteins. It is important for the survival and pathogenesis of S. aureus as it is involved in the regulation of purine and pyrimidine biosynthesis, cell wall metabolism, autolysis, virulence, and antibiotic resistance. M. tuberculosis PknB is essential for growth and it acts on diverse substrates including proteins involved in peptidoglycan synthesis, cell division, transcription, stress responses, and metabolic regulation. B. subtilis PrkC is located at the inner membrane of endospores and functions to trigger spore germination. Bacterial STKs in this subfamily show varied domain architectures. The well-characterized members such as S. aureus and M. tuberculosis PknB, and B. subtilis PrkC, contain an N-terminal cytosolic kinase domain, a transmembrane (TM) segment, and mutliple C-terminal extracellular PASTA domains. The PknB subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
pfam05738, Cna_B, Cna protein B-type domain. This domain is found in Staphylococcus aureus collagen-binding surface protein. The structure of the repetitive B-region has been solved and forms a beta sandwich structure.
cd13123, MATE_MurJ_like, MurJ/MviN, a subfamily of the multidrug and toxic compound extrusion (MATE)-like proteins. Escherichia coli MurJ (MviN) has been identified as essential for murein biosynthesis. It has been suggested that MurJ functions as the peptidoglycan lipid II flippase which is involved in translocation of lipid-anchored peptidoglycan precursors across the cytoplasmic membrane, though results obtained in Bacillus subtilis seem to indicate that its MurJ homologs are not essential for growth. Some MviN family members (e.g. in Mycobacterium tuberculosis) possess an extended C-terminal region that contains an intracellular pseudo-kinase domain and an extracellular domain resembling carbohydrate-binding proteins. Proteins from the MATE family are involved in exporting metabolites across the cell membrane and are often responsible for multidrug resistance (MDR).
cd06564, GH20_DspB_LnbB-like, Glycosyl hydrolase family 20 (GH20) catalytic domain of dispersin B (DspB), lacto-N-biosidase (LnbB) and related proteins. Dispersin B is a soluble beta-N-acetylglucosamidase found in bacteria that hydrolyzes the beta-1,6-linkages of PGA (poly-beta-(1,6)-N-acetylglucosamine), a major component of the extracellular polysaccharide matrix. Lacto-N-biosidase hydrolyzes lacto-N-biose (LNB) type I oligosaccharides at the nonreducing terminus to produce lacto-N-biose as part of the GNB/LNB (galacto-N-biose/lacto-N-biose I) degradation pathway. The lacto-N-biosidase from Bifidobacterium bifidum has this GH20 domain, a carbohydrate binding module 32, and a bacterial immunoglobulin-like domain 2, as well as a YSIRK signal peptide and a G5 membrane anchor at the N and C termini, respectively. The GH20 hexosaminidases are thought to act via a catalytic mechanism in which the catalytic nucleophile is not provided by solvent or the enzyme, but by the substrate itself.
pfam07555, NAGidase, beta-N-acetylglucosaminidase. This family has previously been described as a hyaluronidase. However, more recently it has been shown that this family has beta-N-acetylglucosaminidase activity.
cd05801, PGM_like3, This bacterial PGM-like (phosphoglucomutase-like) protein of unknown function belongs to the alpha-D-phosphohexomutase superfamily. The alpha-D-phosphohexomutases include several related enzymes that catalyze a reversible intramolecular phosphoryl transfer on their sugar substrates. Other members of this superfamily include phosphoglucosamine mutase (PNGM), phosphoacetylglucosamine mutase (PAGM), the bacterial phosphomannomutase ManB, the bacterial phosphoglucosamine mutase GlmM, and the bifunctional phosphomannomutase/phosphoglucomutase (PMM/PGM). Each of these enzymes has four domains with a centrally located active site formed by four loops, one from each domain. All four domains are included in this alignment model.
cd02570, PseudoU_synth_EcTruA, Eukaryotic and bacterial pseudouridine synthases similar to E. coli TruA. This group consists of eukaryotic and bacterial pseudouridine synthases similar to E. coli TruA, Pseudomonas aeruginosa truA and human pseudouridine synthase-like 1 (PUSL1). Pseudouridine synthases catalyze the isomerization of specific uridines in an RNA molecule to pseudouridines (5-ribosyluracil, psi). No cofactors are required. E. coli TruA makes psi38/39 and/or 40 in tRNA. psi38 and psi39 in tRNAs are highly phylogenetically conserved. P. aeruginosa truA is required for induction of type III secretory genes and may act through modifying tRNAs critical for the expression of type III genes or their regulators.
pfam14403, CP_ATPgrasp_2, Circularly permuted ATP-grasp type 2. Circularly permuted ATP-grasp prototyped by Roseiflexus RoseRS_2616 that is associated in gene neighborhoods with a GCS2-like COOH-NH2 ligase, alpha/beta hydrolase fold peptidase, GAT-II -like amidohydrolase, and M20 peptidase. Members of this family are predicted to be involved in the biosynthesis of small peptides.
cd09278, RNase_HI_prokaryote_like, RNase HI family found mainly in prokaryotes. Ribonuclease H (RNase H) is classified into two evolutionarily unrelated families, type 1 (prokaryotic RNase HI, eukaryotic RNase H1 and viral RNase H) and type 2 (prokaryotic RNase HII and HIII, and eukaryotic RNase H2). RNase H is an endonuclease that cleaves the RNA strand of an RNA/DNA hybrid in a sequence non-specific manner. RNase H is involved in DNA replication, repair and transcription. RNase H is widely present in various organisms, including bacteria, archaea and eukaryotes and most prokaryotic and eukaryotic genomes contain multiple RNase H genes. Despite the lack of amino acid sequence homology, type 1 and type 2 RNase H share a main-chain fold and steric configurations of the four acidic active-site (DEDD), residues and have the same catalytic mechanism and functions in cells. One of the important functions of RNase H is to remove Okazaki fragments during DNA replication. Prokaryotic RNase H varies greatly in domain structures and substrate specificities. Prokaryotes and some single-cell eukaryotes do not require RNase H for viability.
