The halo-opsin gene. I. Identification and isolation.

Halorhodopsin (HR), the light-driven chloride pump in halobacteria, was purified in the denatured as well as in the native state and chemically cleaved into peptide fragments. Isolation of peptide and liquid phase sequencing yielded approximately 20% of the halo-opsin (HO) structure in non-overlapping peptides. Chemically synthesized oligodeoxynucleotides corresponding to a peptide sequence obtained from both HR preparations were used to screen a cosmid gene bank of Halobacterium halobium strain L-33. A positive clone contained cosmid pAB H47 which by subcloning and nucleotide sequencing was shown to encode at least part of the HO gene.