Members of this family are 5-methylthioribose kinases () that catalyse phosphorylation of 5-methylthioribose (MTR), a step in the recycling of methionine from 5'-methylthioadenosine, a co-product of polyamine biosynthesis. The preceding step of methylthioadenosine (MTA) hydrolysis to MTR is catalysed by 5'-methylthioadenosine/S-adenosylhomocysteine (MTA/AdoHcy) nucleosidase.Bacillus subtilis protein MtnK (formerly YkrT) []and Klebsiella pneumoniae protein MtrK []have been experimentally characterised. K. pneumoniae MtrK expression is regulated by methionine [].As this enzyme is absent in mammals, it has been considered a target for rational drug design.
This transmembrane domain is found in many amino acid transporters including (UNC-47) and (MTR). UNC-47 encodes a vesicular amino butyric acid (GABA) transporter, (VGAT) and is is predicted to have 10 transmembrane domains UNC47_CAEEL []. MTR is an N system amino acid transporter system protein involved in methyltryptophan resistance MTR_NEUCR. Other proteins with this domain include proline transporters and amino acid transporters whose specificity has not yet been identified.
The Trp repressor (TrpR) binds to at least five operators in the Escherichia coli genome, repressing gene expression. The operators at which it binds vary considerably in DNA sequence and location within the promoter; when bound to the Trp operon it recognises the sequence 5'-ACTAGT-3' and acts to prevent the initiation of transcription. The TrpR controls the trpEDCBA (trpO) operon and the genes for trpR, aroH, mtr and aroL, which are involved in the biosynthesis and uptake of the amino acid tryptophan []. The repressor binds to the operators only in the presence of L-tryptophan, thereby controlling the intracellular level of its effector; the complex also regulates Trp repressor biosynthesis by binding to its own regulatory region. TrpR acts as a dimer that is composed of identical 6-helical subunits, where four of the helices form the core of the protein and intertwine with the corresponding helices from the other subunit.
The Trp repressor (TrpR) binds to at least five operators in the Escherichia coli genome, repressing gene expression. The operators at which it binds vary considerably in DNA sequence and location within the promoter; when bound to the Trp operon it recognises the sequence 5'-ACTAGT-3' and acts to prevent the initiation of transcription. The TrpR controls the trpEDCBA (trpO) operon and the genes for trpR, aroH, mtr and aroL, which are involved in the biosynthesis and uptake of the amino acid tryptophan []. The repressor binds to the operators only in the presence of L-tryptophan, thereby controlling the intracellular level of its effector; the complex also regulates Trp repressor biosynthesis by binding to its own regulatory region. TrpR acts as a dimer that is composed of identical 6-helical subunits, where four of the helices form the core of the protein and intertwine with the corresponding helices from the other subunit.
The Trp repressor (TrpR) binds to at least five operators in the Escherichia coli genome, repressing gene expression. The operators at which it binds vary considerably in DNA sequence and location within the promoter; when bound to the Trp operon it recognises the sequence 5'-ACTAGT-3' and acts to prevent the initiation of transcription. The TrpR controls the trpEDCBA (trpO) operon and the genes for trpR, aroH, mtr and aroL, which are involved in the biosynthesis and uptake of the amino acid tryptophan []. The repressor binds to the operators only in the presence of L-tryptophan, thereby controlling the intracellular level of its effector; the complex also regulates Trp repressor biosynthesis by binding to its own regulatory region. TrpR acts as a dimer that is composed of identical 6-helical subunits, where four of the helices form the core of the protein and intertwine with the corresponding helices from the other subunit.This entry represents Trp repressors found in proteobacterial and chlamydial species.
The Trp repressor (TrpR) binds to at least five operators in the Escherichia coli genome, repressing gene expression. The operators at which it binds vary considerably in DNA sequence and location within the promoter; when bound to the Trp operon it recognises the sequence 5'-ACTAGT-3' and acts to prevent the initiation of transcription. The TrpR controls the trpEDCBA (trpO) operon and the genes for trpR, aroH, mtr and aroL, which are involved in the biosynthesis and uptake of the amino acid tryptophan []. The repressor binds to the operators only in the presence of L-tryptophan, thereby controlling the intracellular level of its effector; the complex also regulates Trp repressor biosynthesis by binding to its own regulatory region. TrpR acts as a dimer that is composed of identical 6-helical subunits, where four of the helices form the core of the protein and intertwine with the corresponding helices from the other subunit.The bacterial chromosomal replication initiation factor DnaA is a monomeric protein that shows structural similarity to the TrpR, except that it contains additional N-terminal helices. DnaA is a member of the AAA+ family of ATPases, and forms a large, oligomeric assembly at the replication origin site (oriC); the oligomeric complex of DnaA recognises and processes specific origin sequences in order to initiate replication in bacteria [].
Amino acid permeases are integral membrane proteins involved in the transportof amino acids into the cell. A number of such proteins have been found to beevolutionary related [, , ].Aromatic amino acids are concentrated in the cytoplasm of Escherichia coli by 4 distinct transport systems: a general aromatic amino acid permease, and aspecific permease for each of the 3 types (Phe, Tyr and Trp) []. It has been shown []that some permeases in E. coli and related bacteria are evolutionary related.These permeases are proteins of about 400 to 420 amino acids and are located in the cytoplasmic membrane and, like bacterial sugar/cation transporters, are thought to contain 12 transmembrane (TM)regions []- hydropathy analysis, however, is inconclusive, suggesting thepossibility of 10 to 12 membrane-spanning domains []. The best conserved domain is a stretch of 20 residues which seems to be located in a cytoplasmic loop between thefirst and second transmembrane region.This family is specific for aromatic amino acid transporters and includes the tyrosine permease, TyrP (), and the tryptophan transporters TnaB () and Mtr () of E. coli.
