Studies on the Biosynthesis of Bacterio-opsin. Demonstration of the Existence of Protein Species Structurally Related to Bacterio-opsin

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Abstract
The kinetics of processing newly synthesized bacterio-opsin from the non-crystalline state within the brown membrane to the crystalline state within the [Halobacterium halobium] purple membrane was followed by pulse-chase experiments. Biosynthesis of bacterio-opsin was highly resistant to RNA-synthesis inhibitors like rifampicin and ethidium bromide. In the presence of ethidium bromide, only 5 protein species continue to be synthesized in halobacteria, one of them being bacterio-opsin. In spheroplasts, synthesis of bacterio-opsin is selectively disturbed. The purple membrane isolated from spheroplasts contains new, additional protein species with apparent MW of 19,000, 23,000 and 29,000. These proteins share common amino acid sequences with bacterio-opsin. In the halobacterial cell membrane, 2 membrane proteins with apparent MW of 30,000 and 36,000 were detected which are structurally related to bacterio-opsin. Bacterio-opsin and the 30,000 MW and 36,000 MW proteins contain covalently bound sulfate.