TIGR02002, PTS_system_glucose-specific_IIABC_component, PTS system, glucose-specific IIBC component. This model represents the combined B and C domains of the PTS transport system enzyme II specific for glucose transport. Many of the genes in this family also include an A domain as part of the same polypeptide and thus should be given the name "PTS system, glucose-specific IIABC component" while the B. subtilus enzyme also contains an enzyme III domain which appears to act independently of the enzyme II domains. This family is most closely related to the N-acetylglucosamine-specific PTS enzymes (TIGR01998). [Transport and binding proteins, Carbohydrates, organic alcohols, and acids].
TIGR01448, recD_rel, helicase, putative, RecD/TraA family. This model describes a family similar to RecD, the exodeoxyribonuclease V alpha chain of TIGR01447. Members of this family, however, are not found in a context of RecB and RecC and are longer by about 200 amino acids at the amino end. Chlamydia muridarum has both a member of this family and a RecD. [Unknown function, Enzymes of unknown specificity].
cd00854, NagA, N-acetylglucosamine-6-phosphate deacetylase, NagA, catalyzes the hydrolysis of the N-acetyl group of N-acetyl-glucosamine-6-phosphate (GlcNAc-6-P) to glucosamine 6-phosphate and acetate. This is the first committed step in the biosynthetic pathway to amino-sugar-nucleotides, which is needed for cell wall peptidoglycan and teichoic acid biosynthesis. Deacetylation of N-acetylglucosamine is also important in lipopolysaccharide synthesis and cell wall recycling.
cd01968, Nitrogenase_NifE_I, Nitrogenase_NifE_I: a subgroup of the NifE subunit of the NifEN complex: NifE forms an alpha2beta2 tetramer with NifN. NifE and NifN are structurally homologous to nitrogenase MoFe protein alpha and beta subunits respectively. NifEN participates in the synthesis of the iron-molybdenum cofactor (FeMoco) of the MoFe protein. NifB-co (an iron and sulfur containing precursor of the FeMoco) from NifB is transferred to the NifEN complex where it is further processed to FeMoco. The NifEN bound precursor of FeMoco has been identified as a molybdenum-free, iron- and sulfur- containing analog of FeMoco. It has been suggested that this NifEN bound precursor also acts as a cofactor precursor in nitrogenase systems which require a cofactor other than FeMoco: i.e. iron-vanadium cofactor (FeVco) or iron only cofactor (FeFeco).
pfam11255, DUF3054, Protein of unknown function (DUF3054). Some members in this family of proteins are annotated as membrane proteins however this cannot be confirmed. Currently no function is known.
cd10437, GIY-YIG_HE_I-TevI_like, N-terminal catalytic domain of GIY-YIG intron endonuclease I-TevI, I-BmoI, I-BanI, I-BthII and similar proteins. I-TevI is a site-specific GIY-YIG homing endonuclease encoded within the group I intron of the thymidylate synthase gene (td) from Escherichia coli phage T4. It functions as an endonuclease that catalyzes the first step in intron homing by generating a double-strand break in the intronless td allele within a sequence designated the homing site. I-TevI recognizes its extensive 37 base pair DNA target in a site-specific, but sequence-tolerant manner. The cleavage site is located at 23 (upper strand) and 25 (lower strand) nucleotides upstream of the intron insertion site. A divalent cation, such as Mg2+, is required for the catalysis. I-TevI also acts as a repressor of its own transcription. It binds an operator that is located upstream of the I-TevI coding sequence and overlaps the T4 late promoter, which drives I-TevI expression from within the td intron. I-TevI binds the homing sites and the operator with the same affinity, but cleaves the homing site more efficiently than the operator. I-TevI consists of an N-terminal catalytic domain, containing the GIY-YIG motif, and a C-terminal DNA-binding domain that binds DNA as a monomer, joined by a flexible linker. The C-terminal domain includes three subdomains: a zinc finger, a minor-groove binding alpha-helix (NUMOD3, nuclease-associated modular domain 3), and a helix-turn-helix domain (HTH). The last two are responsible for DNA-binding. The zinc finger is part of the linker and not required for DNA-binding. It is implicated as a distance sensor to constrain the catalytic domain to cleave the homing site at a fixed position. None of other GIY-YIG endonucleases have been found to have the zinc finger motif. This family also includes a reduced activity isoschizomer of I-TevI, I-BmoI, which is encoded within the group I intron of the thymidylate synthase (TS) gene (thyA) from Bacillus mojavensis. I-BmoI catalyzes the first step in intron homing by generating a double-strand break in the intronless td allele within a sequence designated the homing site in the presence of a divalent cation cofactor, such as Mg2+. In the absence of Mg2+, I-Bmol only nicks one of the strands. Both I-BmoI and I-TevI bind a homologous stretch of TS-encoding DNA as monomers, but use different strategies to distinguish intronless from intron-containing substrates. I-TevI recognizes substrates at the level of DNA-binding. However, I-BmoI binds both intron-containing and intronless TS-encoding substrates, but efficiently cleaves only intronless substrate. Afterwards they cleave their respective intronless substrates in the same positions, and both require a critical G-C base pair adjacent to the top strand site for efficient cleavage. The C-terminal domain of I-BmoI has nuclease-associated modular DNA-binding domains (NUMODs), but lacks the zinc finger, which is different from that of I-TevI. Although the zinc finger implicated as a distance determination in I-TevI is absent, I-BmoI still possesses some cleavage distance discrimination. Besides I-TevI and I-BmoI, this family contains a putative GIY-YIG homing endonuclease, I-BanI, encoded within the self-splicing group I intron of nrdE gene from Bacillus anthracis. It contains two major domains, the N-terminal GIY-YIG domain and the C-terminal DNA-binding domain that consists of a minor-groove DNA binding alpha-helix motif and a helix-turn-helix (HTH) motif. I-BanI generates a double-strand break (DSB) in the intronless nrdE gene. The cleavage site is located at 5 and 7 nucleotides upstream of the intron insertion site, with 2-nucleotide 3' extensions. The recognition site is 35 to 40 base pairs and covers the cleavage site with a bias toward the downstream region including the (intervening sequence) IVS insertion site. Moreover, this family contains another putative GIY-YIG homing endonuclease, I-BthII, encoded within the self-splicing group I intron of nrdF gene from Bacillus thuringiensis ssp. pakistani. It contains a GIY-YIG motif that generates a double-strand break (DSB) in the intronless nrdF gene. The cleavage site is located at 7 and 9 nucleotides upstream of the intron insertion site, leaving 2-nucleotide 3' extensions. The recognition site is 27 to 29 base pairs with the DSB cleavage site at the 5'-end of the top strand, and with the intervening sequence (IVS) insertion site approximately in the middle of the recognition site.
TIGR03534, RF_mod_PrmC, protein-(glutamine-N5) methyltransferase, release factor-specific. Members of this protein family are HemK (PrmC), a protein once thought to be involved in heme biosynthesis but now recognized to be a protein-glutamine methyltransferase that modifies the peptide chain release factors. All members of the seed alignment are encoded next to the release factor 1 gene (prfA) and confirmed by phylogenetic analysis. SIMBAL analysis (manuscript in prep.) shows the motif [LIV]PRx[DE]TE (in Escherichia coli, IPRPDTE) confers specificity for the release factors rather than for ribosomal protein L3. [Protein fate, Protein modification and repair].
