The precursor of PsaD assembles into the photosystem I complex in two steps

Limor Minai, Yuval Cohen, Parag R. Chitnis, Rachel Nechushtai*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


The present study addresses the assembly in the chloroplast thylakoid membranes of PsaD, a peripheral membrane protein of the photosystem I complex. Located on the stromal side of the thylakoids, PsaD was found to assemble in vitro into the membranes in its precursor (pre-PsaD) and also in its mature (PsaD) form. Newly assembled unprocessed pre-PsaD was resistant to NaBr and alkaline wash. Yet it was sensitive to proteolytic digestion. In contradistinction, when the assembled precursor was processed, the resulting mature PsaD was resistant to proteases to the same extent endogeneous PsaD. The accumulation of protease-resistant PsaD in the thylakoids correlated with the increase of mature-PsaD in the membranes. This protection of mature PsaD from proteolysis could not be observed when PsaD was in a soluble form-i.e. not assembled within the thylakoids. The data suggest that pre-PsaD assembles to the membranes and only in a second step processing takes place. The observation that the assembly of pre-PsaD is affected by salts to a much lesser extent than that of mature-PsaD supports a two-step assembly of pre- PsaD.

Original languageAmerican English
Pages (from-to)6338-6342
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number13
StatePublished - 25 Jun 1996


  • peripheral membrane proteins
  • protein folding
  • thylakoids


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