Effect of tunicamycin on the glycosylation of rhodopsin |
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Authors: | James J. Plantner Louis Poncz Edward L. Kean |
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Affiliation: | 1. The Lorand V. Johnson Laboratory for Research in Ophthalmology, Department of Surgery, Division of Ophthalmology, Cleveland, Ohio 44106 U.S.A.;2. The Department of Biochemistry, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106 U.S.A. |
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Abstract: | The incorporation of [3H]glucosamine, [3H]mannose, and [35S]methionine into rhodopsin was investigated in retinas which had been incubated in the presence and absence of the antibiotic, tunicamycin. In its presence, the incorporation of glucosamine was inhibited 70% and mannose, 96% compared to controls. In the presence of tunicamycin the attachment of glucosamine to core-region sites was virtually eliminated. The formation of unglycosylated rhodopsin was also indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and concanavalin A-Sepharose chromatography. These findings are consistent with the participation of the lipid-linked pathway in the glycosylation of this well-characterized intrinsic glycoprotein of the membranes of the disk of the rod outer segment. As indicated by the incorporation of [35S]methionine, the synthesis of rhodopsin apoprotein was inhibited by a much lesser amount. This suggests that the glycosylation of rhodopsin is not required for its insertion into the disk membrane. |
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Keywords: | To whom reprint requests should be addressed at the Laboratory for Eye Research Room 653 Wearn Research Building Case Western Reserve University Cleveland Ohio 44106. |
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