![]() Toc159 and Toc34 are GTPases regulated by phosphorylation. The translocon for preprotein transport across the outer envelope consists of three precursor binding proteins with known or proposed functions, Toc34, Toc159 and Toc64 ( translocon of the outer envelope of chloroplasts for a review, see Kessler and Schnell, 2004 Soll and Schleiff, 2004). Cytosolic Hsp70 is generally involved in the folding of newly synthesised proteins ( Bukau et al, 2000 Young et al, 2004), and its association seems to be required to keep the preproteins in an import competent unfolded state ( Soll and Schleiff, 2004). It was postulated that 14-3-3 proteins together with Hsp70 form a guidance complex for targeting of phosphorylated preproteins to the chloroplast surface ( May and Soll, 2000). of the small subunit of RubisCO (pSSU)) enhances the import rate presumably through interaction with 14-3-3 proteins. In case of chloroplasts, it is proposed that phosphorylation of some transit peptides (e.g. While the translocation process itself is understood in some molecular detail, the mechanism by which the preproteins are transferred from the cytosol to the Toc translocon remains still elusive. Most chloroplast proteins are nuclear encoded, synthesised on cytosolic ribosomes as precursor proteins, and imported into the organelle via translocation complexes in the outer and inner envelope membrane of chloroplasts ( Jarvis and Robinson, 2004 Kessler and Schnell, 2004 Soll and Schleiff, 2004).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |