A polyferredoxin with eight [4Fe-4S] clusters as a subunit of molybdenum formylmethanofuran dehydrogenase from Methanosarcina barkeri

作者：Vorholt JA; Vaupel M; Thauer RK

来源：European Journal of Biochemistry, 1996, 236(1): 309-317.

DOI：10.1111/j.1432-1033.1996.t01-1-00309.x

• methanogenic Archaea
• Methanosarcina
• molybdenum enzymes
• molybdopterin
• iron-sulfur proteins

Formylmethanofuran dehydrogenase (Fmd) from Methanosarcina barkeri is a molybdenum iron-sulfur protein involved in methanogenesis. The enzyme contains approximately 30 mel non-heme iron/mol and 30 mol acid-labile sulfur/mol. We report here the cloning and sequencing of the encoding genes, and that these genes form a transcription unit findEFACDB. Evidence is provided that the subunit FmdB harbours the molybdenum-containing active site and may bind one [4Fe-4S] cluster. fmdF encodes a protein with four tandemly repeated bacterial-ferredoxin-like domains and is predicted to be a polyferredoxin that could contain as many as 32 iron atoms in eight [4Fe-4S] clusters. The other genes code for proteins without sequence motifs characteristic for iron-sulfur proteins. These findings suggest that most of the iron-sulfur clusters present in the purified formylmethanofuran dehydrogenase are associated with the subunit FmdF The finding that FmdF forms a tight complex with the other subunits of formylmethanofuran dehydrogenase indicates a function of the polyferredoxin in the reaction catalyzed by the enzyme. fmdE encodes a protein not present in the purified enzyme. All six genes of the find operon were expressed in Escherichia coli and yielded proteins of expected molecular masses. A malE-findF gene fusion was constructed and expressed in E. coli, making the apoprotein of the polyferredoxin available in preparative amounts.

• 出版日期1996-2-15