cd07516, HAD_Pase, phosphatase, similar to Escherichia coli Cof and Thermotoga maritima TM0651; belongs to the haloacid dehalogenase-like superfamily. Escherichia coli Cof is involved in the hydrolysis of HMP-PP (4-amino-2-methyl-5-hydroxymethylpyrimidine pyrophosphate, an intermediate in thiamin biosynthesis), Cof also has phosphatase activity against the coenzymes pyridoxal phosphate (PLP) and FMN. Thermotoga maritima TM0651 acts as a phosphatase with a phosphorylated carbohydrate molecule as a possible substrate. Escherichia coli YbhA is also a member of this family and catalyzes the dephosphorylation of PLP, YbhA can also hydrolyze erythrose-4-phosphate and fructose-1,6-bis-phosphate. Members of this family belong to the haloacid dehalogenase-like (HAD) hydrolases, a large superfamily of diverse enzymes that catalyze carbon or phosphoryl group transfer reactions on a range of substrates, using an active site aspartate in nucleophilic catalysis. Members of this superfamily include 2-L-haloalkanoic acid dehalogenase, azetidine hydrolase, phosphonoacetaldehyde hydrolase, phosphoserine phosphatase, phosphomannomutase, P-type ATPases and many others. HAD hydrolases are found in all three kingdoms of life, and most genomes are predicted to contain multiple HAD-like proteins. Members possess a highly conserved alpha/beta core domain, and many also possess a small cap domain, the fold and function of which is variable. HAD hydrolases are sometimes referred to as belonging to the DDDD superfamily of phosphohydrolases.
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.
TIGR04056, OMP_RagA_SusC, TonB-linked outer membrane protein, SusC/RagA family. This model describes a distinctive clade among the TonB-linked outer membrane proteins (OMP). Members of this family are restricted to the Bacteriodetes lineage (except for Gemmatimonas aurantiaca T-27 from the novel phylum Gemmatimonadetes) and occur in high copy numbers, with over 100 members from Bacteroides thetaiotaomicron VPI-5482 alone. Published descriptions of members of this family are available for RagA from Porphyromonas gingivalis, SusC from Bacteroides thetaiotaomicron, and OmpW from Bacteroides caccae. Members form pairs with members of the SusD/RagB family (pfam07980). Transporter complexes including these outer membrane proteins are likely to import large degradation products of proteins (e.g. RagA) or carbohydrates (e.g. SusC) as nutrients, rather than siderophores. [Transport and binding proteins, Unknown substrate].
pfam03100, CcmE, CcmE. CcmE is the product of one of a cluster of Ccm genes that are necessary for cytochrome c biosynthesis in eubacteria. Expression of these proteins is induced when the organisms are grown under anaerobic conditions with nitrate or nitrite as the final electron acceptor.
cd10326, SLC5sbd_NIS-like, Na(+)/iodide (NIS) and Na(+)/multivitamin (SMVT) cotransporters, and related proteins; solute binding domain. NIS (product of the SLC5A5 gene) transports I-, and other anions including ClO4-, SCN-, and Br-. SMVT (product of the SLC5A6 gene) transports biotin, pantothenic acid and lipoate. This subfamily also includes SMCT1 and 2. SMCT1(the product of the SLC5A8 gene) is a high-affinity transporter of various monocarboxylates including lactate and pyruvate, short-chain fatty acids, ketone bodies, nicotinate and its structural analogs, pyroglutamate, benzoate and its derivatives, and iodide. SMCT2 (product of the SLC5A12 gene) is a low-affinity transporter for short-chain fatty acids, lactate, pyruvate, and nicotinate. This subfamily belongs to the solute carrier 5 (SLC5) transporter family.
cd05334, DHPR_SDR_c_like, dihydropteridine reductase (DHPR), classical (c) SDRs. Dihydropteridine reductase is an NAD-binding protein related to the SDRs. It converts dihydrobiopterin into tetrahydrobiopterin, a cofactor necessary in catecholamines synthesis. Dihydropteridine reductase has the YXXXK of these tyrosine-dependent oxidoreductases, but lacks the typical upstream Asn and Ser catalytic residues. SDRs are a functionally diverse family of oxidoreductases that have a single domain with a structurally conserved Rossmann fold (alpha/beta folding pattern with a central beta-sheet), an NAD(P)(H)-binding region, and a structurally diverse C-terminal region. Classical SDRs are typically about 250 residues long, while extended SDRS are approximately 350 residues. Sequence identity between different SDR enzymes are typically in the 15-30% range, but the enzymes share the Rossmann fold NAD-binding motif and characteristic NAD-binding and catalytic sequence patterns. These enzymes have a 3-glycine N-terminal NAD(P)(H)-binding pattern (typically, TGxxxGxG in classical SDRs and TGxxGxxG in extended SDRs), while substrate binding is in the C-terminal region. A critical catalytic Tyr residue (Tyr-151, human 15-hydroxyprostaglandin dehydrogenase (15-PGDH) numbering), is often found in a conserved YXXXK pattern. In addition to the Tyr and Lys, there is often an upstream Ser (Ser-138, 15-PGDH numbering) and/or an Asn (Asn-107, 15-PGDH numbering) or additional Ser, contributing to the active site. Substrates for these enzymes include sugars, steroids, alcohols, and aromatic compounds. The standard reaction mechanism is a proton relay involving the conserved Tyr and Lys, as well as Asn (or Ser). Some SDR family members, including 17 beta-hydroxysteroid dehydrogenase contain an additional helix-turn-helix motif that is not generally found among SDRs.
pfam01578, Cytochrom_C_asm, Cytochrome C assembly protein. This family consists of various proteins involved in cytochrome c assembly from mitochondria and bacteria; CycK from Rhizobium, CcmC from E. coli and Paracoccus denitrificans and orf240 from wheat mitochondria. The members of this family are probably integral membrane proteins with six predicted transmembrane helices. It has been proposed that members of this family comprise a membrane component of an ABC (ATP binding cassette) transporter complex. It is also proposed that this transporter is necessary for transport of some component needed for cytochrome c assembly. One member CycK contains a putative heme-binding motif, orf240 also contains a putative heme-binding motif and is a proposed ABC transporter with c-type heme as its proposed substrate. However it seems unlikely that all members of this family transport heme nor c-type apocytochromes because CcmC in the putative CcmABC transporter transports neither. CcmF forms a working module with CcmH and CcmI, CcmFHI, and itself is unlikely to bind haem directly.
pfam12893, Lumazine_bd_2, Putative lumazine-binding. This is a family of uncharacterized proteins. However, the family belongs to the NTF2-like superfamily of various enzymes, and some of the members of the family are putative dehydrogenases.
smart00089, PKD, Repeats in polycystic kidney disease 1 (PKD1) and other proteins. Polycystic kidney disease 1 protein contains 14 repeats, present elsewhere such as in microbial collagenases.
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.
TIGR01361, DAHP_synth_Bsub, 3-deoxy-7-phosphoheptulonate synthase. This model describes one of at least three types of phospho-2-dehydro-3-deoxyheptonate aldolase (DAHP synthase). This enzyme catalyzes the first of 7 steps in the biosynthesis of chorismate, that last common precursor of all three aromatic amino acids and of PABA, ubiquinone and menaquinone. Some members of this family, including an experimentally characterized member from Bacillus subtilis, are bifunctional, with a chorismate mutase domain N-terminal to this region. The member of this family from Synechocystis PCC 6803, CcmA, was shown to be essential for carboxysome formation. However, no other candidate for this enzyme is present in that species, chorismate biosynthesis does occur, other species having this protein lack carboxysomes but appear to make chorismate, and a requirement of CcmA for carboxysome formation does not prohibit a role in chorismate biosynthesis. [Amino acid biosynthesis, Aromatic amino acid family].
cd13631, PBP2_Ct-PDT_like, Catalytic domain of prephenate dehydratase from Chlorobium tepidum and similar proteins, subgroup 2; the type 2 periplasmic binding protein fold. Prephenate dehydratase (PDT, EC:4.2.1.51) converts prephenate to phenylpyruvate through dehydration and decarboxylation reactions. PDT plays a key role in the biosynthesis of L-Phe in organisms that utilize the shikimate pathway. PDT is allosterically regulated by L-Phe and other amino acids. The catalytic PDT domain consists of two similar subdomains with a cleft in between, which hosts the highly conserved active site. In gram-postive bacteria and archaea, PDT is a monofunctional enzyme, consisting of a catalytic domain (PDT domain) and a regulatory domain (ACT) (aspartokinase, chorismate mustase domain). In gram-negative bacteria, PDT exists as fusion protein with chorismate mutase (CM), forming a bifunctional enzyme, P-protein (PheA). The CM in the P-protein catalyzes the pericycle isomerization of chorismate to prephenate that serves as a substrate for PDT. The CM and PDT are essentail enzymes for the biosynthesis of aromatic amino acids in microorganisms but are not found in humans. Thus, both CM and PDT can potentially serve as drug targets against microbial pathogens. The PDT domain has the same structural fold as the type 2 periplasmic binding proteins (PBP2), many of which are involved in chemotaxis and uptake of nutrients and other small molecules from the extracellular space as a primary receptor. The PBP2 proteins are typically comprised of two globular subdomains connected by a flexible hinge and bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap.
cd03896, M20_PAAh_like, M20 Peptidases, Poly(aspartic acid) hydrolase-like proteins. Peptidase M20 family, Poly(aspartic acid) hydrolase (PAA hydrolase)-like subfamily. PAA hydrolase enzymes are involved in alpha,beta-poly(D,L-aspartic acid) (tPAA) biodegradation. PAA is being extensively studied as a replacement for commercial polycarboxylate components since it can be degraded by enzymes from isolated tPAA degrading bacteria. Thus far, two types of PAA degrading bacteria (Sphingomonas sp. KT-1 and Pedobacter sp. KP-2) have been investigated in detail; the former can completely degrade tPAA of low-molecular weights below 5000, while the latter can degrade high molecular weight tPAA to release oligo(aspartic acid) (OAA) as a product, suggesting two kinds of PAA degrading enzymes. It has been shown that PAA hydrolase-1 from Sphingomonas sp. KT-1 hydrolyzes beta,beta-aspartic acid units in tPAA to produce OAA, and it is suggested that PAA hydrolase-2 hydrolyzes OAA to aspartic acid. Also included in this family is Bradyrhizobium 5-nitroanthranilic acid (5NAA)-aminohydrolase (5NAA-A), a biodegradation enzyme that converts 5NAA to 5-nitrosalicylic acid; 5NAA is a metabolite secreted by Streptomyces scabies, the bacterium responsible for potato scab, and metabolized by Bradyrhizobium species strain JS329.
pfam14487, DUF4433, Domain of unknown function (DUF4433). This family of proteins is found in bacteria, archaea and eukaryotes. Proteins in this family are typically between 201 and 230 amino acids in length. There is a single completely conserved residue E that may be functionally important. This family is distantly similar to pfam01885 suggesting these may be ADP-ribosylases.
cd08195, DHQS, Dehydroquinate synthase (DHQS) catalyzes the conversion of DAHP to DHQ in shikimate pathway for aromatic compounds synthesis. Dehydroquinate synthase (DHQS) catalyzes the conversion of 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) to dehydroquinate (DHQ) in the second step of the shikimate pathway. This pathway, which involves seven sequential enzymatic steps in the conversion of erythrose 4-phosphate and phosphoenolpyruvate into chorismate for subsequent synthesis of aromatic compounds, is found in bacteria, microbial eukaryotes, and plants, but not in mammals. Therefore, enzymes of this pathway are attractive targets for the development of non-toxic antimicrobial compounds, herbicides and anti-parasitic agents. The activity of DHQS requires nicotinamide adenine dinucleotide (NAD) as cofactor. A single active site in DHQS catalyzes five sequential reactions involving alcohol oxidation, phosphate elimination, carbonyl reduction, ring opening, and intramolecular aldol condensation. The binding of substrates and ligands induces domain conformational changes. In some fungi and protozoa, this domain is fused with the other four domains in shikimate pathway and forms a penta-domain AROM protein, which catalyzes steps 2-6 in the shikimate pathway.
cd06588, PhnB_like, Escherichia coli PhnB and similar proteins. The Escherichia coli phnB gene is found next to an operon of fourteen genes (phnC-to-phnP) related to the cleavage of carbon-phosphorus (C-P) bonds in unactivated alkylphosphonates, supporting bacterial growth on alkylphosphonates as the sole phosphorus source. It was originally considered part of that operon. PhnB appears to play no direct catalytic role in the usage of alkylphosphonate. Although many of the proteins in this family have been annotated as 3-demethylubiquinone-9 3-methyltransferase enzymes by automatic annotation programs, the experimental evidence for this assignment is lacking. In Escherichia coli, the gene coding 3-demethylubiquinone-9 3-methyltransferase enzyme is ubiG, which belongs to the AdoMet-MTase protein family. PhnB-like proteins adopt a structural fold similar to bleomycin resistance proteins, glyoxalase I, and type I extradiol dioxygenases.
cd07197, nitrilase, Nitrilase superfamily, including nitrile- or amide-hydrolyzing enzymes and amide-condensing enzymes. This superfamily (also known as the C-N hydrolase superfamily) contains hydrolases that break carbon-nitrogen bonds; it includes nitrilases, cyanide dihydratases, aliphatic amidases, N-terminal amidases, beta-ureidopropionases, biotinidases, pantotheinase, N-carbamyl-D-amino acid amidohydrolases, the glutaminase domain of glutamine-dependent NAD+ synthetase, apolipoprotein N-acyltransferases, and N-carbamoylputrescine amidohydrolases, among others. These enzymes depend on a Glu-Lys-Cys catalytic triad, and work through a thiol acylenzyme intermediate. Members of this superfamily generally form homomeric complexes, the basic building block of which is a homodimer. These oligomers include dimers, tetramers, hexamers, octamers, tetradecamers, octadecamers, as well as variable length helical arrangements and homo-oligomeric spirals. These proteins have roles in vitamin and co-enzyme metabolism, in detoxifying small molecules, in the synthesis of signaling molecules, and in the post-translational modification of proteins. They are used industrially, as biocatalysts in the fine chemical and pharmaceutical industry, in cyanide remediation, and in the treatment of toxic effluent. This superfamily has been classified previously in the literature, based on global and structure-based sequence analysis, into thirteen different enzyme classes (referred to as 1-13). This hierarchy includes those thirteen classes and a few additional subfamilies. A putative distant relative, the plasmid-borne TraB family, has not been included in the hierarchy.
TIGR02168, Chromosome_partition_protein_Smc, chromosome segregation protein SMC, common bacterial type. SMC (structural maintenance of chromosomes) proteins bind DNA and act in organizing and segregating chromosomes for partition. SMC proteins are found in bacteria, archaea, and eukaryotes. This family represents the SMC protein of most bacteria. The smc gene is often associated with scpB (TIGR00281) and scpA genes, where scp stands for segregation and condensation protein. SMC was shown (in Caulobacter crescentus) to be induced early in S phase but present and bound to DNA throughout the cell cycle. [Cellular processes, Cell division, DNA metabolism, Chromosome-associated proteins].
