cd00424, PolY, Y-family of DNA polymerases. Y-family DNA polymerases are a specialized subset of polymerases that facilitate translesion synthesis (TLS), a process that allows the bypass of a variety of DNA lesions. Unlike replicative polymerases, TLS polymerases lack proofreading activity and have low fidelity and low processivity. They use damaged DNA as templates and insert nucleotides opposite the lesions. The active sites of TLS polymerases are large and flexible to allow the accomodation of distorted bases. Most TLS polymerases are members of the Y-family, including Pol eta, Pol kappa/IV, Pol iota, Rev1, and Pol V, which is found exclusively in bacteria. In eukaryotes, the B-family polymerase Pol zeta also functions as a TLS polymerase. Expression of Y-family polymerases is often induced by DNA damage and is believed to be highly regulated. TLS is likely induced by the monoubiquitination of the replication clamp PCNA, which provides a scaffold for TLS polymerases to bind in order to access the lesion. Because of their high error rates, TLS polymerases are potential targets for cancer treatment and prevention.
TIGR03599, YloV, DAK2 domain fusion protein YloV. This model describes a protein family that contains an N-terminal DAK2 domain (pfam02734), so named because of similarity to the dihydroxyacetone kinase family family. The GTP-binding protein CgtA (a member of the obg family) is a bacterial GTPase associated with ribosome biogenesis, and it has a characteristic extension (TIGR03595) in certain lineages. This protein family described here was found, by the method of partial phylognetic profiling, to have a phylogenetic distribution strongly correlated to that of TIGR03595. This correlation implies some form of functional coupling.
TIGR00762, DegV, EDD domain protein, DegV family. This family of proteins is related to DegV of Bacillus subtilis and includes paralogous sets in several species (B. subtilis, Deinococcus radiodurans, Mycoplasma pneumoniae) that are closer in percent identity to each than to most homologs from other species. This suggests both recent paralogy and diversity of function. DegV itself is encoded immediately downstream of DegU, a transcriptional regulator of degradation, but is itself uncharacterized. Crystallography suggested a lipid-binding site, while comparison of the crystal structure to dihydroxyacetone kinase and to a mannose transporter EIIA domain suggests a conserved domain, EDD, with phosphotransferase activity. [Unknown function, General].
TIGR04078, radical_SAM_domain_protein_protein, peptide modification radical SAM enzyme, YydG family. Members of this radical SAM protein family for peptide modification occur only in the context of members of family TIGR04077, which average about 50 amino acids in length. In Bacillus subtilis, this protein (YydG) appears to act on its cognate target peptide (YydF) prior to its export, and result in the creation of a signaling molecule that induces the LiaRS two-component system. [Regulatory functions, Protein interactions].
cd01158, SCAD_SBCAD, Short chain acyl-CoA dehydrogenases and eukaryotic short/branched chain acyl-CoA dehydrogenases. Short chain acyl-CoA dehydrogenase (SCAD). SCAD is a mitochondrial beta-oxidation enzyme. It catalyzes the alpha,beta dehydrogenation of the corresponding trans-enoyl-CoA by FAD, which becomes reduced. The reduced form of SCAD is reoxidized in the oxidative half-reaction by electron-transferring flavoprotein (ETF), from which the electrons are transferred to the mitochondrial respiratory chain coupled with ATP synthesis. This subgroup also contains the eukaryotic short/branched chain acyl-CoA dehydrogenase(SBCAD), the bacterial butyryl-CoA dehydorgenase(BCAD) and 2-methylbutyryl-CoA dehydrogenase, which is involved in isoleucine catabolism. These enzymes are homotetramers.
TIGR02274, Probable_deoxycytidine_triphosphate_deaminase, deoxycytidine triphosphate deaminase. Members of this family include the Escherichia coli monofunctional deoxycytidine triphosphate deaminase (dCTP deaminase) and a Methanocaldococcus jannaschii bifunctional dCTP deaminase (3.5.4.13)/dUTP diphosphatase (EC 3.6.1.23), which has the EC number 3.5.4.30 for the overall operation. [Purines, pyrimidines, nucleosides, and nucleotides, 2'-Deoxyribonucleotide metabolism].
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.
