Biophysics of structure and mechanism

, Volume 3, Issue 2, pp 199–203 | Cite as

Isoelectric focusing of phosphorylated cattle rhodopsin

  • Hermann Kühn
  • J. Hugh McDowell


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 words

Rhodopsin Isoelectric focusing Phosphorylation Membrane proteins 

Abbreviations used


moles of phosphate per mole of rhodopsin


rod outer segments


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Copyright information

© Springer-Verlag 1977

Authors and Affiliations

  • Hermann Kühn
    • 1
  • J. Hugh McDowell
    • 1
  1. 1.Institut für NeurobiologieKernforschungsanlage Jülich GmbHJülich 1Federal Republic of Germany

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