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The gene product of the Halobacterium salinarum htrVIII gene is a 642 amino acid transmembrane protein with six domains embedded in the cell membrane. The structure of the membrane spanning segments of HTRVII protein resemble the heme binding region of cytochrome c oxidase while the carboxyl terminus exhibit homology with a methyl-accepting chemotaxis protein. HTRVII belongs to the B subfamily of transducer proteins in the genus Halobacterium.

The primary structure and function of the HtrXI halobacterial putative transducer was analyzed during the fractionation of Halobacter salinarum proteins. Cell fractionation experiments indicated that soluble character of the archeal HtrXI transducer protein which was also involved in cellular signal transduction. Furthermore, htrXI deletion mutants exhibited defective chemotactic responses due to the absence of the halobacterial putative transducer which recognizes chemoeffectors.

EmrR is the repressor of the emrRAB operon of Escherichia coli. It was purified to 95% homogeneity and was observed to bind putative ligands of the EmrAB pump, 2,4-dinitrophenol, carbonyl cyanide m-chlorophenylhydrazone and carbonyl cyanide p-(trifluoro-methoxy)phenylhydrazone, with affinities in the micromolecular range. Equilibrium dialysis experiments indicated one bound ligand per monomer of the dimeric EmrR protein.

Research was conducted to show that the sensory rhodopsin II transducer HtrII is also responsible for serine chemotaxis in the archaeon Halobacterium salinarum. Using an agarose-in-plug bridge method, it is shown that an HtrII overexpression strain has a quicker response to serine than does an HtrII deletion strain. Moreover, an in vivo flow assay demonstrates that the deletion strain is unable to modulate methylesterase activity after serine addition of photostimulation.