Covalent modification of rhodopsin with imidoesters: evidence for transmembrane arrangement of rhodopsin in rod outer segment disk membranes
- 1 May 1980
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 19 (10), 2067-2074
- https://doi.org/10.1021/bi00551a010
Abstract
The transmembrane disposition of the visual pigment rhodopsin was studied by the covalent labeling of protein amino groups with membrane-permeable and -impermeable imidoesters. A new, highly reactive permeable reagent, 2-(methylsulfonyl)ethyl acetimidate (SAI) was developed. The permeabilities of this compound and the impermeable reagent isethionyl acetimidate (IAI) across the rod outer segment disc membrane were directly measured. Rhodopsin apparently contains 3 classes of amino groups. One class (35-55% of the total) reacts rapidly with the membrane-impermeable reagent and is presumably exposed on the outside surface of the membrane. A 2nd class (35-55% of the total) is located on the internal surface of the disc since its rate of reaction is dependent on the relative permeabilities of the labeling reagents. The remaining 10% of the rhodopsin amino groups are inaccessible to either type of imidate and are largely accounted for by the single lysine residue which specificially binds the chromophore retinal. Freeze-fracture EM and the above properties imply rhodopsin is a transmembrane protein.This publication has 14 references indexed in Scilit:
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