AN ARCHAEAL AEROTAXIS TRANSDUCER COMBINES SUBUNIT-I CORE STRUCTURES OF EUKARYOTIC CYTOCHROME-C-OXIDASE AND EUBACTERIAL METHYL-ACCEPTING CHEMOTAXIS PROTEINS

Signal transduction in the archaeon Halobacterium salinarum is mediate d by three distinct subfamilies of transducer proteins. Here we report the complete htrVIII gene sequence and present analysis of the encode d primary structure and its functional features. HtrVIII is a 642-amin o-acid protein and belongs to halobacterial transducer subfamily B. At the N terminus, the protein contains six transmembrane segments that exhibit homology to the heme-binding sites of the eukaryotic cytochrom e c oxidase. The C-terminal domain has high homology with the eubacter ial methyl-accepting chemotaxis protein. The HtrVIII protein mediates aerotaxis: a strain with a deletion of the htrVIII gene loses aerotaxi s, while an overproducing strain exhibits stronger aerotaxis. We also demonstrate that HtrVIII is a methyl-accepting protein and demethylate s during the aerotaxis response.