Identification of a primary in vivo degradation product of the rapidly-turning-over 32 kd protein of photosystem II

EMBO J. 1987 Oct;6(10):2865-9.

Abstract

The 32 kd photosystem II protein of plant chloroplasts is rapidly turned over in the light. The initial events in the degradation of the 32 kd protein were studied. A 23.5 kd breakdown product was identified in Spirodela oligorrhiza membranes using immunological analysis. The 23.5 kd polypeptide was shown to be derived from the amino-terminal portion of the 32 kd protein using partial proteolytic fingerprinting. An in vivo precursor--product relationship between the 32 kd protein and the 23.5 kd polypeptide was kinetically demonstrated by radiolabeling and pulse-chase experiments. The cleavage site yielding the 23.5 kd polypeptide was localized to a functionally active region (between helices IV and V) of the 32 kd protein. We propose that an alpha-helix-destabilizing 'degradation' sequence, bordered by arginine residues 225 and 238, is involved in the formation of the 23.5 kd polypeptide.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Chlorophyll / metabolism*
  • Chloroplasts / metabolism
  • Hydrolysis
  • Kinetics
  • Light
  • Light-Harvesting Protein Complexes
  • Macromolecular Substances
  • Molecular Weight
  • Peptide Hydrolases / metabolism
  • Photosynthetic Reaction Center Complex Proteins
  • Photosystem II Protein Complex
  • Plant Proteins / metabolism*
  • Plants / metabolism*

Substances

  • Light-Harvesting Protein Complexes
  • Macromolecular Substances
  • Photosynthetic Reaction Center Complex Proteins
  • Photosystem II Protein Complex
  • Plant Proteins
  • Chlorophyll
  • Peptide Hydrolases