MOLECULAR CHAPERONES ARE PRESENT IN THE THYLAKOID LUMEN OF PEA-CHLOROPLASTS

A soluble protein fraction was obtained from pea chloroplast thylakoid s, which represents highly enriched lumenal components, Using antisera against chaperonin 60 (cpn60), chaperonin 10 (cpn10) and the heat sho ck cognate protein of 70 kDa (hsc70) we are able to demonstrate, that the thylakoid lumen contains a separate set of molecular chaperones, w hich is distinct from the stromal one, In contrast to the alpha and be ta subunits of cpn60 present in the stroma the lumen contains only one cpn60 isoform of distinct isoelectric paint, Furthermore the lumenal cpn10 is of 'normal' size and not like its stromal counterpart of a do uble-domain tandem architecture, The immunoreactive hsc70 isoforms in the lumen seem also to be different from the stromal ones, Thus, chlor oplasts seem to contain the largest number of molecular chaperone isof orms present in one organelle.