Chloroplasts make use of translocon complexes in the outer and inner plastid envelope membranes called the TOC and TIC machineries for importing the major part of their proteins from the cytosol. Using the chloroplast envelope quinone oxidoreductase homologue ceQORH as model, we recently showed that import of this transit sequence-less precursor into Arabidopsis chloroplasts occurs through a unique pathway. Import of ceQORH is mediated by three distinct chloroplast members of the preprotein and amino acid transporter (PRAT) family, designated HP20, HP30 and HP30-2. This family comprises 17 evolutionarily conserved preprotein and amino acid transporters that obviously operate both in mitochondria and chloroplasts and mediate the import of certain subsets of cytosolic precursor proteins including those lacking cleavable transit sequences.
For more information : Reinbothe S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permitsunrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.