Chemical rescue of a site-modified ligand to a [4Fe-4S] cluster in PsaC, a bacterial-like dicluster ferredoxin bound to Photosystem I.
Biochim Biophys Acta
; 1767(6): 712-24, 2007 Jun.
Article
em En
| MEDLINE
| ID: mdl-17434441
ABSTRACT
Chemical rescue of site-modified amino acids using externally supplied organic molecules represents a powerful method to investigate structure-function relationships in proteins. Here we provide definitive evidence that aryl and alkyl thiolates, reagents typically used for in vitro iron-sulfur cluster reconstitutions, serve as rescue ligands to a site-specifically modified [4Fe-4S](1+,2+) cluster in PsaC, a bacterial dicluster ferredoxin-like subunit of Photosystem I. PsaC binds two low-potential [4Fe-4S](1+,2+) clusters termed F(A) and F(B). In the C13G/C33S variant of PsaC, glycine has replaced cysteine at position 13 creating a protein that is missing one of the ligating amino acids to iron-sulfur cluster F(B). Using a variety of analytical techniques, including non-heme iron and acid-labile sulfur assays, and EPR, resonance Raman, and Mössbauer spectroscopies, we showed that the C13G/C33S variant of PsaC binds two [4Fe-4S](1+,2+) clusters, despite the absence of one of the biological ligands. (19)F NMR spectroscopy indicated that the external thiolate replaces cysteine 13 as a substitute ligand to the F(B) cluster. The finding that site-modified [4Fe-4S](1+,2+) clusters can be chemically rescued with external thiolates opens new opportunities for modulating their properties in proteins. In particular, it provides a mechanism to attach an additional electron transfer cofactor to the protein via a bound, external ligand.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Complexo de Proteína do Fotossistema I
/
Proteínas Ferro-Enxofre
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
Estados Unidos