Oxaloacetate synthesis in the methanarchaeon Methanosarcina barkeri: pyruvate carboxylase genes and a putative Escherichia coli-type bifunctional biotin protein ligase gene (bpl/birA) exhibit a unique organization.
J Bacteriol
; 183(12): 3804-10, 2001 Jun.
Article
em En
| MEDLINE
| ID: mdl-11371547
ABSTRACT
Evidence is presented that, in Methanosarcina barkeri oxaloacetate synthesis, an essential and major CO(2) fixation reaction is catalyzed by an apparent alpha(4)beta(4)-type acetyl coenzyme A-independent pyruvate carboxylase (PYC), composed of 64.2-kDa biotinylated and 52.9-kDa ATP-binding subunits. The purified enzyme was most active at 70 degrees C, insensitive to aspartate and glutamate, mildly inhibited by alpha-ketoglutarate, and severely inhibited by ATP, ADP, and excess Mg(2+). It showed negative cooperativity towards bicarbonate at 70 degrees C but not at 37 degrees C. The organism expressed holo-PYC without an external supply of biotin and, thus, synthesized biotin. pycA, pycB, and a putative bpl gene formed a novel operon-like arrangement. Unlike other archaeal homologs, the putative biotin protein ligases (BPLs) of M. barkeri and the closely related euryarchaeon Archaeoglobus fulgidus appeared to be of the Escherichia coli-type (bifunctional, with two activities BirA or a repressor of the biotin operon and BPL). We found the element Tyr(Phe)ProX(5)Phe(Tyr) to be fully conserved in biotin-dependent enzymes; it might function as the hinge for their "swinging arms."
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Piruvato Carboxilase
/
Proteínas Repressoras
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Proteínas de Bactérias
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Fatores de Transcrição
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Methanosarcina barkeri
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Carbono-Nitrogênio Ligases
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Ácido Oxaloacético
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Proteínas de Escherichia coli
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Genes Bacterianos
Idioma:
En
Revista:
J Bacteriol
Ano de publicação:
2001
Tipo de documento:
Article
País de afiliação:
Estados Unidos