The amino‐ and carboxyl‐terminal sequence of bovine rhodopsin

Abstract

The amino terminus of bovine rhodopsin is blocked and has the sequence x-Met-Asn(CHO)-Gly-Thr-Glu-Gly-Pro-Asn-Phe-Tyr-Val-Pro-Phe-Ser-Asn(CHO)-Lys-Thr-Gly-Val-Val-Arg, where CHO represents sites of carbohydrate attachment. The carboxyl-terminal sequence of rhodopsin is Val-Ser-Lys-Thr-Glu-Thr-Ser-Gln-Val-Ala-Pro-Ala. Upon short-term digestion of rod outer segment (ROS) membranes with thermolysin, opsin (∼ 35,000 daltons) is converted to a membrane-bound fragment O′ (∼ 30,500 daltons) and 2 peptides containing 12 amino acids are released from the carboxyl terminus of rhodopsin into the supernatant. Upon long-term digestion of ROS with thermolysin, opsin and O′ are replaced by the membrane-bound fragments F₁ (∼25,000 daltons), and F₂ (∼9,500 daltons). When ³²P-ROS are digested, F₂ carries the ³²P. Both O′ and F₁ contain the amino-terminal glycopeptide.