Involvement of a chloroplast HSP70 heat shock protein in the integration of a protein (light-harvesting complex protein precursor) into the thylakoid membrane

Shaul Yalovsky, Harald Paulsen, Dorit Michaeli, Parag R. Chitnis, Rachel Nechushtai*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

Molecular chaperones, including those belonging to the 70-kDa family of heat shock proteins (HSP70), assist both the translocation of proteins across membranes and their assembly into oligomeric complexes. We purified a chloroplast HSP70 (ct-HSP70) and demonstrated that it plays a major role in the insertion of the precursor of the major light-harvesting complex of photos v stem II (pLHCP; an integral membrane protein) into the thylakoids (the inner membranes of the chloroplast). Addition of the purified ct-HSP70 is necessary for efficient insertion of pLHCP into isolated thylakoid membranes. This activity of the purified ct-HSP70 is similar to that previously reported for the total stromal extract. When the chloroplast stromal extract is depleted of HSP70, a correlative reduction in the insertion activity of pLHCP is observed. The interaction between the ct-HSP70 and pLHCP involves physical association. The purified HSP70 acts directly on the membrane protein, presumably prevents its refolding, and thereby helps to maintain its competence for insertion into membranes.

Original languageAmerican English
Pages (from-to)5616-5619
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume89
Issue number12
StatePublished - 1992

Keywords

  • Biogenesis
  • Chaperone
  • Membrane integration

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