GenePage for the cmoB gene of Escherichia coli K-12

Primary Gene Name: cmoB
EcoGene Accession Number: EG14034
K-12 Gene Accession Number: ECK1872
MG1655 Gene Identifier: b1871
Gene Name Mnemonic: CarboxylMethOxy
Alternate Gene Symbols: yecP
Description: tRNA (cmo5U34)-carboxymethyltransferase, carboxy-SAM-dependent
  # bp Upstream # bp Downstream
MW: 37006.57 ---------323 aa Pre-Run BlastP UniProt
Pre-Run BlastP NR+Env
Left End: 1953442
Left Intergenic Region

Name: cmoA_cmoB

Length: 4 bp overlap

Orientation: Codirectional+

Left_end: 1953442

Right_end: 1953445

Centisome: 42.09

Genomic Address
Minute or Centisome (%) = 42.09
Right End: 1954413
Right Intergenic Region

Name: cmoB_torZ

Length: 164 bp gap

Orientation: Convergent

Left_end: 1954414

Right_end: 1954577

Centisome: 42.11

The carboxymethyltransferase CmoB utilizes the novel SAM derivative carboxy-SAM to convert 5-hydroxyuridine (ho5U34) to 5-oxyacetyl uridine (cmo5U34) in tRNA; the enzymes responsible for making ho5U and mcmoU5 are unknown (Kim, 2013). Two alternatives were proposed for the synthesis of cmo5U from ho5U in E. coli including the direct conversion by an acetylase (actually a carboxymethyltransferase) and a two-step reaction with mo5U as an intermediate; mo5U34 is present in the U wobble base of tRNAs from B. subtilis (Murao, 1978). In S. typhimurium, CmoA, a member of the methyltransferase superfamily, was previously thought to be involved in the chorismate-dependent conversion of mo5U34 to cmo5U34 in tRNA as both ho5U and mo5U accumulated in a cmoA mutant and in an aroD mutant, although a mechanism was not apparent; CmoB was previously thought to be responsible for the conversion of ho5U to mo5U since only ho5U accumulated in a cmoB mutants (Nasvall, 2004). Now it seems from work done in E. coli, that since mo5U is not an intermediate in (m)cmo5U synthesis, CmoB might utilize SAM inefficiently in the absence of CmoA-generated carboxy-SAM to form mo5U from ho5U. It is also possible that mcmo5U is made from cmo5U by CmoB utilizing SAM instead of carboxy-SAM.

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