cd07185, OmpA_C-like, Peptidoglycan binding domains similar to the C-terminal domain of outer-membrane protein OmpA. OmpA-like domains (named after the C-terminal domain of Escherichia coli OmpA protein) have been shown to non-covalently associate with peptidoglycan, a network of glycan chains composed of disaccharides, which are crosslinked via short peptide bridges. Well-studied members of this family include the Escherichia coli outer membrane protein OmpA, the Escherichia coli lipoprotein PAL, Neisseria meningitdis RmpM, which interact with the outer membrane, as well as the Escherichia coli motor protein MotB, and the Vibrio flagellar motor proteins PomB and MotY, which interact with the inner membrane.
cd00616, AHBA_syn, 3-amino-5-hydroxybenzoic acid synthase family (AHBA_syn). AHBA_syn family belongs to pyridoxal phosphate (PLP)-dependent aspartate aminotransferase superfamily (fold I). The members of this CD are involved in various biosynthetic pathways for secondary metabolites. Some well studied proteins in this CD are AHBA_synthase, protein product of pleiotropic regulatory gene degT, Arnb aminotransferase and pilin glycosylation protein. The prototype of this family, the AHBA_synthase, is a dimeric PLP dependent enzyme. AHBA_syn is the terminal enzyme of 3-amino-5-hydroxybenzoic acid (AHBA) formation which is involved in the biosynthesis of ansamycin antibiotics, including rifamycin B. Some members of this CD are involved in 4-amino-6-deoxy-monosaccharide D-perosamine synthesis. Perosamine is an important element in the glycosylation of several cell products, such as antibiotics and lipopolysaccharides of gram-positive and gram-negative bacteria. The pilin glycosylation protein encoded by gene pglA, is a galactosyltransferase involved in pilin glycosylation. Additionally, this CD consists of ArnB (PmrH) aminotransferase, a 4-amino-4-deoxy-L-arabinose lipopolysaccharide-modifying enzyme. This CD also consists of several predicted pyridoxal phosphate-dependent enzymes apparently involved in regulation of cell wall biogenesis. The catalytic lysine which is present in all characterized PLP dependent enzymes is replaced by histidine in some members of this CD.
pfam13585, CHU_C, C-terminal domain of CHU protein family. The function of this C-terminal domain is not known; there are several conserved tryptophan and asparagine residues.
cd05247, UDP_G4E_1_SDR_e, UDP-glucose 4 epimerase, subgroup 1, extended (e) SDRs. UDP-glucose 4 epimerase (aka UDP-galactose-4-epimerase), is a homodimeric extended SDR. It catalyzes the NAD-dependent conversion of UDP-galactose to UDP-glucose, the final step in Leloir galactose synthesis. This subgroup has the characteristic active site tetrad and NAD-binding motif of the extended SDRs. Extended SDRs are distinct from classical SDRs. In addition to the Rossmann fold (alpha/beta folding pattern with a central beta-sheet) core region typical of all SDRs, extended SDRs have a less conserved C-terminal extension of approximately 100 amino acids. Extended SDRs are a diverse collection of proteins, and include isomerases, epimerases, oxidoreductases, and lyases; they typically have a TGXXGXXG cofactor binding motif. SDRs are a functionally diverse family of oxidoreductases that have a single domain with a structurally conserved Rossmann fold, an NAD(P)(H)-binding region, and a structurally diverse C-terminal region. Sequence identity between different SDR enzymes is typically in the 15-30% range; they catalyze a wide range of activities including the metabolism of steroids, cofactors, carbohydrates, lipids, aromatic compounds, and amino acids, and act in redox sensing. Classical SDRs have an TGXXX[AG]XG cofactor binding motif and a YXXXK active site motif, with the Tyr residue of the active site motif serving as a critical catalytic residue (Tyr-151, human 15-hydroxyprostaglandin dehydrogenase numbering). In addition to the Tyr and Lys, there is often an upstream Ser and/or an Asn, contributing to the active site; while substrate binding is in the C-terminal region, which determines specificity. The standard reaction mechanism is a 4-pro-S hydride transfer and proton relay involving the conserved Tyr and Lys, a water molecule stabilized by Asn, and nicotinamide. Atypical SDRs generally lack the catalytic residues characteristic of the SDRs, and their glycine-rich NAD(P)-binding motif is often different from the forms normally seen in classical or extended SDRs. Complex (multidomain) SDRs such as ketoreductase domains of fatty acid synthase have a GGXGXXG NAD(P)-binding motif and an altered active site motif (YXXXN). Fungal type ketoacyl reductases have a TGXXXGX(1-2)G NAD(P)-binding motif.
cd18097, SpoU-like, SAM-dependent rRNA or tRNA methylase related to SpoU. RNA 2'-O ribose methyltransferase catalyzes the methyltransfer from S-adenosyl-L-methionine (AdoMet) to the 2'-OH group of ribose in tRNA or rRNA. It is part of the SpoU family of MTases, a subfamily of the SPOUT methyltransferase superfamily. The SPOUT methyltransferase superfamily is a large class of S-adenosyl-L-methionine (AdoMet or SAM)-dependent RNA MTases which are structurally characterized by a deep trefoil knot.
cd06529, S24_LexA-like, Peptidase S24 LexA-like proteins are involved in the SOS response leading to the repair of single-stranded DNA within the bacterial cell. This family includes: the lambda repressor CI/C2 family and related bacterial prophage repressor proteins; LexA (EC 3.4.21.88), the repressor of genes in the cellular SOS response to DNA damage; MucA and the related UmuD proteins, which are lesion-bypass DNA polymerases, induced in response to mitogenic DNA damage; RulA, a component of the rulAB locus that confers resistance to UV, and RuvA, which is a component of the RuvABC resolvasome that catalyzes the resolution of Holliday junctions that arise during genetic recombination and DNA repair. The LexA-like proteins contain two-domains: an N-terminal DNA binding domain and a C-terminal domain (CTD) that provides LexA dimerization as well as cleavage activity. They undergo autolysis, cleaving at an Ala-Gly or a Cys-Gly bond, separating the DNA-binding domain from the rest of the protein. In the presence of single-stranded DNA, the LexA, UmuD and MucA proteins interact with RecA, activating self cleavage, thus either derepressing transcription in the case of LexA or activating the lesion-bypass polymerase in the case of UmuD and MucA. The LexA proteins are serine proteases that carry out catalysis using a serine/lysine dyad instead of the prototypical serine/histidine/aspartic acid triad found in most serine proteases. LexA sequence homologs are found in almost all of the bacterial genomes sequenced to date, covering a large number of phyla, suggesting both, an ancient origin and a widespread distribution of lexA and the SOS response.
TIGR03916, hypothetical_protein, putative DNA modification/repair radical SAM protein. This uncharacterized protein of about 400 amino acids in length contains a radical SAM protein in the N-terminal half. Members are present in about twenty percent of prokaryotic genomes, always paired with a member of the conserved hypothetical protein TIGR03915. Roughly forty percent of the members of that family exist as fusions with a uracil-DNA glycosylase-like region, TIGR03914. In DNA, uracil results from deamidation of cytosine, forming U/G mismatches that lead to mutation, and so uracil-DNA glycosylase is a DNA repair enzyme. This indirect connection, and the recurring role or radical SAM protein in modification chemistries, suggest that this protein may act in DNA modification, repair, or both. [Unknown function, Enzymes of unknown specificity].
pfam09365, DUF2461, Conserved hypothetical protein (DUF2461). Members of this family are widely (though sparsely) distributed bacterial proteins, about 230 residues in length. All members have a motif RxxRDxRFxxx[DN]KxxY. The function of this protein family is unknown.
TIGR03915, putative_DNA_metabolism_protein, probable DNA metabolism protein. This model represents a conserved hypothetical protein that almost invariably pairs with an uncharacterized radical SAM protein. The pair occurs in about twenty percent of completed prokaryotic genomes. About forty percent of the members of this family occur as fusion proteins, where the C-terminal domain belongs to the uracil-DNA glycosylase family, a DNA repair family (because uracil in DNA is deamidated cytosine). The linkage by gene clustering and correlated species distribution to a radical SAM protein, and by gene fusion to a DNA repair protein family, suggests a role in DNA modification and/or repair.
pfam11751, PorP_SprF, Type IX secretion system membrane protein PorP/SprF. This entry describes a protein family unique to, and greatly expanded in, the Bacteriodetes. Species in this lineage include several, such as Cytophaga hutchinsonii and Cytophaga johnsonae (Flavobacterium johnsoniae), that exhibit a poorly understood rapid gliding phenotype. Several members of this protein family are found in operons with other genes whose loss leads to a loss of the rapid gliding phenotype.
