Structure and orientation of halorhodopsin in the membrane: a proteolytic fragmentation study.

摘要: Abstract Halorhodopsin (HR), the light-driven chloride pump in halobacteria, was digested with various proteolytic enzymes. As expected, carboxypeptidase A removed 14 amino acids from C-terminal tail of detergent-solubilized HR, producing a fragment 25.2 kd size. Membrane-associated HR could be as well, but not right-side-out sealed cell envelope vesicles. We conclude, therefore, that orientation cytoplasmic membrane is such faces side. Tryptic digestion resulted removal same segment, also production two more cleavage products (molecular masses 20.9 and 16.8 respectively). These sites were determined by acid sequencing newly produced N termini, they turned out to within interhelical loops an earlier proposed structural model for HR. Incubation chymotrypsin thermolysin yielded different cleavage, regions which accessible on surface protein. Since results show three six loop segments contain sites, support