title: Assembly of functional rhodopsin requires a disulfide bond between cysteine residues 110 and 187.
abstract: Cysteine residues 110 and 187 are essential for the formation of the correct bovine rhodopsin structure (Karnik, S. S., Sakmar, T. P., Chen, H.-B., and Khorana, H. G. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, 8459-8463). We now show that the sulfhydryl groups of these 2 cysteine residues interact to form a disulfide bond. Rhodopsin mutants containing cysteine----serine substitutions were prepared as follows. In one mutant, CysVII, all the 10 cysteine residues of rhodopsin were replaced by serines. A second mutant, CysVIII, contained only C110 and C185; a third mutant, CysIX, contained only C185 and C187 while the fourth mutant, CysX, contained only C110 and C187. Only mutant CysX formed functional rhodopsin. Mutants CysVIII and CysIX reacted with [3H]iodoacetic acid showing the presence of free sulfhydryl groups while mutant CysX was inert to this reagent. CysX reacted with cyanide ion to form a thiocyanate derivative showing the presence of a disulfide bond. The C110-C187 disulfide bond is buried in rhodopsin because reactions with disulfide reducing agents and cyanide ion require prior treatment with denaturants.
authors: Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
authors: S S
authors: SS
authors: Karnik
authors: H G
authors: HG
authors: Khorana
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003545:Cysteine; D004220:Disulfides / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D011487:Protein Conformation; D012243:Rhodopsin / Q000235:genetics* / Q000378:metabolism; D017299:Rod Opsins
chemical_list: D004220:Disulfides; D005136:Eye Proteins; D015345:Oligonucleotide Probes; D017299:Rod Opsins; D012243:Rhodopsin; D003545:Cysteine