Sequence and electron paramagnetic resonance analyses of nitrate reductase NarGH from a denitrifying halophilic euryarchaeote Haloarcula marismortui

Abstract

Genes encoding the NarG and NarH subunits of the molybdo–iron–sulfur enzyme, a nitrate reductase from a denitrifying halophilic euryarchaeota Haloarcula marismortui, were cloned and sequenced. An incomplete cysteine motif reminiscent of that for a [4Fe–4S] cluster binding was found in the NarG subunit, and complete cysteine arrangements for binding one [3Fe–4S] cluster and three [4Fe–4S] clusters were found in the NarH subunit. In conjunction with chemical, electron paramagnetic resonance, and subcellular localization analyses, we firmly establish that the H. marismortui enzyme is a new archaeal member of the known membrane-bound nitrate reductases whose homologs are found in the bacterial domain.