The methane monooxygenase gene cluster of Methylococcus capsulatus (Bath)

Abstract

Methane is oxidised to methanol in methanotrophic bacteria by the enzyme methane monooxygenase (MMO). Methylococcus capsulatus (Bath) produces a soluble MMO which oxidises a range of aliphatic and aromatic compounds with potential for commercial exploitation. This multicomponent enzyme has been extensively characterised and biochemical data have been used to identify a 12-kb fragment of Methylococcus DNA carrying the structural genes mmoY and mmoZ, coding for the β- and γ-subunits of MMO component A, the methane-binding protein. We now report the complete nucleotide (nt) sequence of mmoX, the gene encoding the α-subunit of component A which is found to be 5′ to mmoY and mmoZ. We also report the complete nt sequence of mmoC which encodes component C, the iron-sulfur flavoprotein of MMO, the N terminus of which is significantly homologous with spinach ferredoxin. The mmo structural genes are clustered within a 7-kb region and are closely linked to two small open reading frames of unknown function.