Isoelectric focusing of phosphorylated cattle rhodopsin
- 37 Downloads
32P-rhodopsin was partially separated by isoelectric focusing into several fractions of different phosphorylation extent. It was found that the incorporated phosphate is not uniformly distributed in a population of rhodopsin molecules. In a preparation with an average phosphorylation extent of 2.4 moles of phosphate per mole of rhodopsin, most of the 32P-phosphate was found in fractions where 4–5 phosphates are bound per rhodopsin, whereas a large fraction of the total rhodopsin was not phosphorylated at all. The maximum number of phosphate binding sites in rhodopsin appears to be at least five.
Key wordsRhodopsin Isoelectric focusing Phosphorylation Membrane proteins
moles of phosphate per mole of rhodopsin
rod outer segments
Unable to display preview. Download preview PDF.
- Bownds, D., Dawes, J., Miller, J., Stahlman, M.: Phosphorylation of frog photoreceptor membranes induced by light. Nature (Lond.) New Biol. 237, 125–127 (1972)Google Scholar
- Huang, H. V., Molday, R. S., Dreyer, W. J.: Isoelectric focusing of rod outer segment membrane proteins. FEBS Lett. 37, 285–290 (1973)Google Scholar
- Kühn, H., Dreyer, W. J.: Light-dependent phosphorylation of rhodopsin by ATP. FEBS Lett. 20, 1–6 (1972)Google Scholar
- Kühn, H., Cook, J. H., Dreyer, W. J.: Phosphorylation of rhodopsin in bovine photoreceptor membranes. A dark reaction after illumination. Biochemistry 12, 2495–2502 (1973)Google Scholar
- McDowell, J. H., Kühn, H.: Light-induced phosphorylation of rhodopsin in cattle photoreceptor membranes: Substrate activation and inactivation. Biochemistry 16 (1977), in pressGoogle Scholar
- Miller, J. A., Paulsen, R.: Phosphorylation and dephosphorylation of frog rod outer segment membranes as part of the visual process. J. biol. Chem. 250, 4427–4432 (1975)Google Scholar
- Papermaster, D. S., Dreyer, W. J.: Rhodopsin content in the outer segment membranes of bovine and frog retinal rods. Biochemistry 13, 2438–2444 (1974)Google Scholar
- Plantner, J. J., Kean, E. L.: On the existence of several isoelectric forms of bovine rhodopsin. Exp. Eye Res. 23, 281–284 (1976)Google Scholar
- Shichi, H., Somers, R. L., O'Brien, P. J.: Phosphorylation of rhodopsin: Most rhodopsin molecules are not phosphorylated. Biochem. biophys. Res. Commun. 61, 217–221 (1974)Google Scholar