The fungal ribonucleases T2 from Aspergillus oryzae, M from Aspergillus saitoi and Rh from Rhizopeus niveus are structurally and functionally related 30 Kd glycoproteins []that cleave the 3'-5' internucleotide linkage of RNA via a nucleotide 2',3'-cyclic phosphate intermediates ().Two histidines residues have been shown [, ]to be involved in the catalytic mechanism of RNase T2 and Rh. These residues and the region around them are highly conserved. This entry represents the conserved region containing the first His active site.
Ribonuclease T2 (RNase T2) is a widespread family of secreted RNases found in every organism examined thus far. This family includes RNase Rh, RNase MC1, RNase LE, and self-incompatibility RNases (S-RNases) [, , , , ]. Plant T2 RNases are expressed during leaf senescence in order to scavenge phosphate from ribonucleotides. They are also expressed in response to wounding or pathogen invasion. S-RNases are thought to prevent self-fertilization by acting as selective cytotoxins of "self"pollen. Generally, RNases have two distinct binding sites: the primary site (B1 site) and the subsite (B2 site), for nucleotides located at the 5'- and 3'- terminal ends of the sissile bond, respectively.The fungal ribonucleases T2 from Aspergillus oryzae, M from Aspergillus saitoi and Rh from Rhizopus niveus are structurally and functionally related 30 Kd glycoproteins []that cleave the 3'-5' internucleotide linkage of RNA via a nucleotide 2',3'-cyclic phosphate intermediate (). Two histidines residues have been shown [, ]to be involved in the catalytic mechanism of RNase T2 and Rh. These residues and the region around them are highly conserved ina number of other RNAses that have been found to be evolutionary related to these fungal enzymes.The structure of ribonuclease T2 is composed of an alpha+beta fold.
Ribonuclease T2 (RNase T2) is a widespread family of secreted RNases found in every organism examined thus far. This family includes RNase Rh, RNase MC1, RNase LE, and self-incompatibility RNases (S-RNases) [, , , , ]. Plant T2 RNases are expressed during leaf senescence in order to scavenge phosphate from ribonucleotides. They are also expressed in response to wounding or pathogen invasion. S-RNases are thought to prevent self-fertilization by acting as selective cytotoxins of "self"pollen. Generally, RNases have two distinct binding sites: the primary site (B1 site) and the subsite (B2 site), for nucleotides located at the 5'- and 3'- terminal ends of the sissile bond, respectively.This entry includes the prokaryotic RNase T2 family members.
Ribonuclease T2 (RNase T2) is a widespread family of secreted RNases found in every organism examined thus far. This family includes RNase Rh, RNase MC1, RNase LE, and self-incompatibility RNases (S-RNases) [, , , , ]. Plant T2 RNases are expressed during leaf senescence in order to scavenge phosphate from ribonucleotides. They are also expressed in response to wounding or pathogen invasion. S-RNases are thought to prevent self-fertilization by acting as selective cytotoxins of "self"pollen. Generally, RNases have two distinct binding sites: the primary site (B1 site) and the subsite (B2 site), for nucleotides located at the 5'- and 3'- terminal ends of the sissile bond, respectively.This entry includes the eukaryotic RNase T2 family members.
Ribonuclease T2 (RNase T2) is a widespread family of secreted RNases found in every organism examined thus far. This family includes RNase Rh, RNase MC1, RNase LE, and self-incompatibility RNases(S-RNases) [, , , , ]. Plant T2 RNases are expressed during leaf senescence in order to scavenge phosphate from ribonucleotides. They are also expressed in response to wounding or pathogen invasion. S-RNases are thought to prevent self-fertilization by acting as selective cytotoxins of "self"pollen. Generally, RNases have two distinct binding sites: the primary site (B1 site) and the subsite (B2 site), for nucleotides located at the 5'- and 3'- terminal ends of the sissile bond, respectively.The fungal ribonucleases T2 from Aspergillus oryzae, M from Aspergillus saitoi and Rh from Rhizopus niveus are structurally and functionally related 30 Kd glycoproteins []that cleave the 3'-5' internucleotide linkage of RNA via a nucleotide 2',3'-cyclic phosphate intermediate (). Two histidines residues have been shown [, ]to be involved in the catalytic mechanism of RNase T2 and Rh. These residues and the region around them are highly conserved in a number of other RNAses that have been found to be evolutionary related to these fungal enzymes.
T-even bacteriophages recognise their cellular receptors with the free ends of their six long tail fibres. The Gp38 protein from bacteriophage T2 and related phages is located at the tip of the tail fibre, where it recognises the host receptor []. OmpC has been identified as the host receptor, and sequence variations appear to be an important determinant of host specificity [].Note this family is not related, either in sequence similairty or function, to the Gp38 protein from bacteriophage T4.
Iodothyronine deiodinase () (DI) []is the vertebrate enzyme responsible for the deiodination ofthe prohormone thyroxine (T4 or 3,5,3',5'-tetraiodothyronine) into the biologically active hormone T3 (3,5,3'-triiodothyronine) and of T3 into the inactive metabolite T2 (3,3'-diiodothyronine). All known DI are proteins of about 250 residues that contain a selenocysteine at their active site. Three types of DI are known, type I is commonly found in the liver and kidney [], type II is essential for providing the brain with the appropriate levels of T3 during the critical period of development, and type III (also known as thyroxine 5-deiodinase) is essential for the regulation of thyroid hormone inactivation during embryological development.
Iodothyronine deiodinase () (DI) []is the vertebrate enzyme responsible for the deiodination ofthe prohormone thyroxine (T4 or 3,5,3',5'-tetraiodothyronine) into the biologically active hormone T3(3,5,3'-triiodothyronine) and of T3 into the inactive metabolite T2 (3,3'-diiodothyronine). All known DI areproteins of about 250 residues that contain a selenocysteine at their active site. Three types of DI areknown, type II is essential for providing the brain with the appropriate levels of T3 during the criticalperiod of development, and type III is essential for the regulation of thyroid hormone inactivation duringembryological development. This signature found in the central part of the enzyme, which contains the active site selenocysteine.
The fungal ribonucleases T2 from Aspergillus oryzae, M from Aspergillus saitoi and Rh from Rhizopeus niveus are structurally and functionally related 30 Kd glycoproteins []that cleave the 3'-5' internucleotide linkage of RNA via a nucleotide 2',3'-cyclic phosphate intermediates ().A number of other RNAses have been found to be evolutionary related to thesefungal enzymes:Self-incompatibility []in flowering plants is often controlled by a single gene (S-gene) that has several alleles. This gene prevents fertilization by self-pollen or by pollen bearing either of the two S- alleles expressed in the style. The self-incompatibility glycoprotein fromseveral higher plants of the solanaceae family has been shown [, ]to be a ribonuclease.Phosphate-starvation induced RNAses LE and LX from tomato []. These twoenzymes are probably involved in a phosphate-starvation rescue system.Escherichia coli periplasmic RNAse I (EC 3.1.27.6) (gene rna) [].Aeromonas hydrophila periplasmic RNAse.Haemophilus influenzae hypothetical protein HI0526. Two histidines residues have been shown [, ]to be involved in the catalytic mechanism of RNase T2 and Rh. These residues and the region around them are highly conserved. This entry represents the conserved region containing the second His active site. This region also contains a cysteine which is known to be involved in disulfide bond formation.
Threonine peptidases are characterised by a threonine nucleophile at the N terminus of the mature enzyme. The threonine peptidases belong to clan PB or are unassigned, clan T-. The type example for this clan is the archaean proteasome beta component of Thermoplasma acidophilum.This group of sequences have a signature that places them in MEROPS peptidase family T2 (clan PB(T)). The glycosylasparaginases () are threonine peptidases. Also in this family is L-asparaginase (), which catalyses the following reaction:L-asparagine + H2O = L-aspartate + NH3Glycosylasparaginase catalyses:N4-(beta-N-acetyl-D-glucosaminyl)-L-asparagine + H(2)O =N-acetyl-beta-glucosaminylamine + L-aspartatecleaving the GlcNAc-Asn bond that links oligosaccharides to asparagine in N-linked glycoproteins. The enzyme is composed of two non-identical alpha/beta subunits joined by strong non-covalent forces and has one glycosylation site located in the alpha subunit []and plays a major role in the degradation of glycoproteins.
Iodothyronine deiodinase () (DI) []is the vertebrate enzyme responsible for the deiodination ofthe prohormone thyroxine (T4 or 3,5,3',5'-tetraiodothyronine) into the biologically active hormone T3 (3,5,3'-triiodothyronine) and of T3 into the inactive metabolite T2 (3,3'-diiodothyronine). All known DI are proteins of about 250 residues that contain a selenocysteine at their active site. Three types of DI are known, type I is commonly found in the liver and kidney [], type II is essential for providing the brain with the appropriate levels of T3 during the critical period of development, and type III (also known as thyroxine 5-deiodinase) is essential for the regulation of thyroid hormone inactivation during embryological development.This entry represents type I and III Iodothyronine deiodinases.
These sequences represent 2',3'-cyclic-nucleotide 2'-phosphodiesterase/3'-nucleotidases; it is a bifunctional enzyme localized to the periplasm of Gram-negative bacteria. 2',3'-cyclic-nucleotide 2'-phosphodiesters are intermediates formed during the hydrolysis of RNA by the ribonuclease I, which is also found in the periplasm, and other enzymes of the RNAse T2 family. Bacteria are unable to transport 2',3'-cyclic-nucleotides into the cytoplasm. 2',3'-cyclic-nucleotide 2'-phosphodiesterase/3'-nucleotidases contains 2 active sites which catalyze the reactions that convert the 2',3'-cyclic-nucleotide into a 3'-nucleotide, which is then converted into nucleic acid and phosphate. Both final products can be transported into the cytoplasm. Thus, it has been suggested that 2',3'-cyclic-nucleotide 2'-phosphodiesterase/3'-nucleotidases have a scavenging function. Experimental evidence indicates that a 2',3'-cyclic-nucleotide 2'-phosphodiesterase/3'-nucleotidase enables Yersinia enterocolitica O:8 to grow on 23-cAMP as a sole source of carbon and energy [].
Viral TNFR homologues include vaccinia virus (VACV) cytokine response modifier E (CrmE) [], an encoded TNFR that shares significant sequence similarity with mammalian type 2 TNF receptors (TNFSFR1B, p75, TNFR type 2) [], a cowpox virus encoded cytokine-response modifier B (CrmB) [], which is a secreted form of TNF receptor that can contribute to the modification of TNF-mediated antiviral processes, and a myxoma virus (MYXV) T2 (M-T2) protein that binds and inhibits rabbit TNF-alpha []. The CrmE structure confirms that the canonical TNFR fold is adopted, but only one of the two "ligand-binding"loops of TNFRSF1A is conserved, suggesting a mechanism for the higher affinity of poxvirusTNFRs for TNFalpha over lymphotoxin-alpha []. CrmB protein specifically binds TNF-alpha and TNF-beta indicating that cowpox virus seeks to invade antiviral processes mediated by TNF. Intracellular M-T2 blocks virus-induced lymphocyte apoptosis via a highly conserved viral preligand assembly domain (vPLAD), which controls receptor signaling competency prior to ligand binding [].This entry represents the N-terminal domain of viral TNFRs. TNF-receptors are modular proteins. The N-terminal extracellular part contains a cysteine-rich region responsible for ligand-binding. This region is composed of small modules of about 40 residues containing 6 conserved cysteines; the number and type of modules can vary in different members of the family [, , ].
