S-Adenosyl-S-carboxymethyl-L-homocysteine: a novel cofactor found in the putative tRNA-modifying enzyme CmoA.
Acta Crystallogr D Biol Crystallogr
; 69(Pt 6): 1090-8, 2013 Jun.
Article
em En
| MEDLINE
| ID: mdl-23695253
ABSTRACT
Uridine at position 34 of bacterial transfer RNAs is commonly modified to uridine-5-oxyacetic acid (cmo(5)U) to increase the decoding capacity. The protein CmoA is involved in the formation of cmo(5)U and was annotated as an S-adenosyl-L-methionine-dependent (SAM-dependent) methyltransferase on the basis of its sequence homology to other SAM-containing enzymes. However, both the crystal structure of Escherichia coli CmoA at 1.73 Å resolution and mass spectrometry demonstrate that it contains a novel cofactor, S-adenosyl-S-carboxymethyl-L-homocysteine (SCM-SAH), in which the donor methyl group is substituted by a carboxymethyl group. The carboxyl moiety forms a salt-bridge interaction with Arg199 that is conserved in a large group of CmoA-related proteins but is not conserved in other SAM-containing enzymes. This raises the possibility that a number of enzymes that have previously been annotated as SAM-dependent are in fact SCM-SAH-dependent. Indeed, inspection of electron density for one such enzyme with known X-ray structure, PDB entry 1im8, suggests that the active site contains SCM-SAH and not SAM.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
S-Adenosil-Homocisteína
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RNA de Transferência
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Transferases de Grupo de Um Carbono
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Proteínas de Escherichia coli
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Escherichia coli
Idioma:
En
Revista:
Acta Crystallogr D Biol Crystallogr
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Reino Unido