A BchD (magnesium chelatase) mutant of rhodobacter sphaeroides synthesizes zinc bacteriochlorophyll through novel zinc-containing intermediates.
J Biol Chem
; 286(23): 20313-22, 2011 Jun 10.
Article
em En
| MEDLINE
| ID: mdl-21502322
ABSTRACT
Heme and bacteriochlorophyll a (BChl) biosyntheses share the same pathway to protoporphyrin IX, which then branches as follows. Fe(2+) chelation into the macrocycle by ferrochelatase results in heme formation, and Mg(2+) addition by Mg-chelatase commits the porphyrin to BChl synthesis. It was recently discovered that a bchD (Mg-chelatase) mutant of Rhodobacter sphaeroides produces an alternative BChl in which Mg(2+) is substituted by Zn(2+). Zn-BChl has been found in only one other organism before, the acidophilic Acidiphilium rubrum. Our objectives in this work on the bchD mutant were to 1) elucidate the Zn-BChl biosynthetic pathway in this organism and 2) understand causes for the low amounts of Zn-BChl produced. The bchD mutant was found to contain a Zn-protoporphyrin IX pool, analogous to the Mg-protoporphyrin IX pool found in the wild type strain. Inhibition of ferrochelatase with N-methylprotoporphyrin IX caused Zn-protoporphyrin IX and Zn-BChl levels to decline by 80-90% in the bchD mutant, whereas in the wild type strain, Mg-protoporphyrin IX and Mg-BChl levels increased by 170-240%. Two early metabolites of the Zn-BChl pathway were isolated from the bchD mutant and identified as Zn-protoporphyrin IX monomethyl ester and divinyl-Zn-protochlorophyllide. Our data support a model in which ferrochelatase synthesizes Zn-protoporphyrin IX, and this metabolite is acted on by enzymes of the BChl pathway to produce Zn-BChl. Finally, the low amounts of Zn-BChl in the bchD mutant may be due, at least in part, to a bottleneck upstream of the step where divinyl-Zn-protochlorophyllide is converted to monovinyl-Zn-protochlorophyllide.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
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Bacterioclorofilas
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Zinco
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Rhodobacter sphaeroides
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Liases
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Modelos Biológicos
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Mutação
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
2011
Tipo de documento:
Article
País de afiliação:
Canadá