Antisuppressor mutation in Escherichia coli defective in biosynthesis of 5-methylaminomethyl-2-thiouridine

Sullivan, M.; Cannon, John F.; Webb, Frances; Bock, Robert M.

doi:10.1128/jb.161.1.368-376.1985

Cited by 89 publications

(29 citation statements)

References 42 publications

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“…This insertion does not abolish osmoregulation but simply elevates expression of malT. Another mutation found in this selection (144) was an insertion (null mutation) in asuE, a gene known to encode a lysine tRNA-modifying enzyme (262). This mutation does not affect malT expression and only dampens the effect of high osmolarity on malK and malE expression.…”

Section: Osmoregulation Of the Maltose Systemmentioning

confidence: 95%

Maltose/Maltodextrin System ofEscherichia coli: Transport, Metabolism, and Regulation

Boos

Shuman

1998

Microbiol Mol Biol Rev

569

350

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SUMMARY The maltose system of Escherichia coli offers an unusually rich set of enzymes, transporters, and regulators as objects of study. This system is responsible for the uptake and metabolism of glucose polymers (maltodextrins), which must be a preferred class of nutrients for E. coli in both mammalian hosts and in the environment. Because the metabolism of glucose polymers must be coordinated with both the anabolic and catabolic uses of glucose and glycogen, an intricate set of regulatory mechanisms controls the expression of mal genes, the activity of the maltose transporter, and the activities of the maltose/maltodextrin catabolic enzymes. The ease of isolating many of the mal gene products has contributed greatly to the understanding of the structures and functions of several classes of proteins. Not only was the outer membrane maltoporin, LamB, or the phage lambda receptor, the first virus receptor to be isolated, but also its three-dimensional structure, together with extensive knowledge of functional sites for ligand binding as well as for phage λ binding, has led to a relatively complete description of this sugar-specific aqueous channel. The periplasmic maltose binding protein (MBP) has been studied with respect to its role in both maltose transport and maltose taxis. Again, the combination of structural and functional information has led to a significant understanding of how this soluble receptor participates in signaling the presence of sugar to the chemosensory apparatus as well as how it participates in sugar transport. The maltose transporter belongs to the ATP binding cassette family, and although its structure is not yet known at atomic resolution, there is some insight into the structures of several functional sites, including those that are involved in interactions with MBP and recognition of substrates and ATP. A particularly astonishing discovery is the direct participation of the transporter in transcriptional control of the mal regulon. The MalT protein activates transcription at all mal promoters. A subset also requires the cyclic AMP receptor protein for transcription. The MalT protein requires maltotriose and ATP as ligands for binding to a dodecanucleotide MalT box that appears in multiple copies upstream of all mal promoters. Recent data indicate that the ATP binding cassette transporter subunit MalK can directly inhibit MalT when the transporter is inactive due to the absence of substrate. Despite this wealth of knowledge, there are still basic issues that require clarification concerning the mechanism of MalT-mediated activation, repression by the transporter, biosynthesis and assembly of the outer membrane and inner membrane transporter proteins, and interrelationships between the mal enzymes and those of glucose and glycogen metabolism.

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Section: Osmoregulation Of the Maltose Systemmentioning

confidence: 95%

Maltose/Maltodextrin System ofEscherichia coli: Transport, Metabolism, and Regulation

Boos

Shuman

1998

Microbiol Mol Biol Rev

569

350

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“…The MnmA (formerly AsuE/ TrmU) enzyme together with the cysteine desulfurase IscS and sulfur transfer mediators TusA-E are required for the thiolation of position 2 of the uridine, leading to 2-thiouridine (s 2 U). [10][11][12][13] The GTP and THF-binding protein MnmE (formerly TrmE) and FAD-binding protein MnmG (formerly GidA) form an a 2 b 2 complex and are believed to act together to form 5-carboxymethylaminomethyl-2-thiouridine (cmnm 5 s 2 U). [14][15][16][17] Finally, cmnm 5 s 2 U is first demodified to 5-aminomethyl-2-thiouridine (nm 5 s 2 U) and subsequently methylated in an S-adenosyl-L-methionine (AdoMet) dependent step to mnm 5 s 2 U.…”

Section: Introductionmentioning

confidence: 99%

Sequence–structure–function analysis of the bifunctional enzyme MnmC that catalyses the last two steps in the biosynthesis of hypermodified nucleoside mnm⁵s²U in tRNA

Roovers¹,

Oudjama²,

Kamińska

et al. 2008

Proteins

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MnmC catalyses the last two steps in the biosynthesis of 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U) in tRNA. Previously, we reported that this bifunctional enzyme is encoded by the yfcK open reading frame in the Escherichia coli K12 genome. However, the mechanism of its activity, in particular the potential structural and functional dependence of the domains responsible for catalyzing the two modification reactions, remains unknown. With the aid of the protein fold-recognition method, we constructed a structural model of MnmC in complex with the ligands and target nucleosides and studied the role of individual amino acids and entire domains by site-directed and deletion mutagenesis, respectively. We found out that the N-terminal domain contains residues responsible for binding of the S-adenosylmethionine cofactor and catalyzing the methylation of nm(5)s(2)U to form mnm(5)s(2)U, while the C-terminal domain contains residues responsible for binding of the FAD cofactor. Further, point mutants with compromised activity of either domain can complement each other to restore a fully functional enzyme. Thus, in the conserved fusion protein MnmC, the individual domains retain independence as enzymes. Interestingly, the N-terminal domain is capable of independent folding, while the isolated C-terminal domain is incapable of folding on its own, a situation similar to the one reported recently for the rRNA modification enzyme RsmC.

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“…The modification of U34 requires many different proteins: MnmA catalyses the thiolation of U34 at the 2 position leading to s 2 U (Sullivan et al , 1985). In the modification pathway, TrmE (also called MnmE), together with the protein GidA (Elseviers et al , 1984; Brégeon et al , 2001), is believed to be involved in the addition of the cmnm group at the 5 position, although the precise role of both proteins in the modification reaction is unknown.…”

Section: Introductionmentioning

confidence: 99%

The structure of the TrmE GTP-binding protein and its implications for tRNA modification

Scrima

Vetter

Armengod³

et al. 2004

EMBO J

146

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TrmE is a 50 kDa guanine nucleotide-binding protein conserved between bacteria and man. It is involved in the modification of uridine bases (U34) at the first anticodon (wobble) position of tRNAs decoding two-family box triplets. The precise role of TrmE in the modification reaction is hitherto unknown. Here, we report the X-ray structure of TrmE from Thermotoga maritima. The structure reveals a three-domain protein comprising the N-terminal a/b domain, the central helical domain and the G domain, responsible for GTP binding and hydrolysis. The N-terminal domain induces dimerization and is homologous to the tetrahydrofolate-binding domain of N,N-dimethylglycine oxidase. Biochemical and structural studies show that TrmE indeed binds formyl-tetrahydrofolate. A cysteine residue, necessary for modification of U34, is located close to the C1-group donor 5-formyl-tetrahydrofolate, suggesting a direct role of TrmE in the modification analogous to DNA modification enzymes. We propose a reaction mechanism whereby TrmE actively participates in the formylation reaction of uridine and regulates the ensuing hydrogenation reaction of a Schiff's base intermediate.

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Antisuppressor mutation in Escherichia coli defective in biosynthesis of 5-methylaminomethyl-2-thiouridine

Cited by 89 publications

References 42 publications

Maltose/Maltodextrin System ofEscherichia coli: Transport, Metabolism, and Regulation

Maltose/Maltodextrin System ofEscherichia coli: Transport, Metabolism, and Regulation

Sequence–structure–function analysis of the bifunctional enzyme MnmC that catalyses the last two steps in the biosynthesis of hypermodified nucleoside mnm⁵s²U in tRNA

The structure of the TrmE GTP-binding protein and its implications for tRNA modification

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Antisuppressor mutation in Escherichia coli defective in biosynthesis of 5-methylaminomethyl-2-thiouridine

Cited by 89 publications

References 42 publications

Maltose/Maltodextrin System ofEscherichia coli: Transport, Metabolism, and Regulation

Maltose/Maltodextrin System ofEscherichia coli: Transport, Metabolism, and Regulation

Sequence–structure–function analysis of the bifunctional enzyme MnmC that catalyses the last two steps in the biosynthesis of hypermodified nucleoside mnm5s2U in tRNA

The structure of the TrmE GTP-binding protein and its implications for tRNA modification

Contact Info

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Sequence–structure–function analysis of the bifunctional enzyme MnmC that catalyses the last two steps in the biosynthesis of hypermodified nucleoside mnm⁵s²U in tRNA