Details

Autor(en) / Beteiligte

• Inglese, J
• Glickman, J F
• Lorenz, W
• Caron, M G
• Lefkowitz, R J

Titel

Isoprenylation of a protein kinase. Requirement of farnesylation/alpha-carboxyl methylation for full enzymatic activity of rhodopsin kinase

Ist Teil von

• The Journal of biological chemistry, 1992-01, Vol.267 (3), p.1422-1425

Ort / Verlag

Bethesda, MD: Elsevier Inc

Erscheinungsjahr

1992

Quelle

Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals

Beschreibungen/Notizen

• The primary structure of bovine rhodopsin kinase (RK), which phosphorylates light-activated rhodopsin (Rho*), terminates with the amino acid sequence Cys558-Val-Leu-Ser561, a motif that has been shown to direct the isoprenylation and alpha-carboxyl methylation of many proteins (e.g. p21Ha-ras). Transient expression of RK in COS-7 cells revealed the presence of two immunoreactive protein species. Consistent with RK being modified by isoprenylation, interconversion of these two species was dependent upon isoprenoid biosynthesis in the cells. Moreover, a serine substitution for Cys558 resulted in a single RK species whose migration on sodium dodecyl sulfate-polyacrylamide gels was identical to that of RK from cells treated with mevinolin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and, thus, of isoprenoid biosynthesis. This finding indicates that isoprenylation of RK requires Cys558. The electrophoretic mobility of isoprenylated RK synthesized in COS-7 cells was identical to that of RK from bovine rod outer segments, suggesting that RK is isoprenylated in vivo. RK was determined to be modified by a farnesyl moiety and alpha-carboxyl-methylated. A time course of Rho* phosphorylation revealed that non-processed RK is approximately 4-fold less active than wild-type RK. This is the first demonstration of isoprenylation/alpha-carboxyl methylation of a protein kinase, and suggests that these modifications markedly influence enzymatic activity in vivo.