Two chloroplastic protein translocation components, Tic110 and Toc75, are conserved in different plastid types from multiple plant species.

Abstract

Most chloroplastic proteins are nuclear-encoded and must be transported into the organelle post-translationally. Proteinaceous components in the outer and inner envelope membranes of chloroplasts responsible for this import process were originally identified from pea seedlings. We sought to determine whether these proteins are conserved among different plant species other than pea and among different plastid types. We analyzed plant EST databases and found the presence of homologues to pea chloroplastic protein translocation components, Tic110 and Toc75, in both monocot and dicot species. Because these clones were obtained from various tissues, their presence in different types of plastids is proposed. Protein extracts were prepared from several plant species and from different plant tissues, and then probed with antisera raised against pea Tic110 and Toc75. The results support the idea that translocation components originally found in pea chloroplasts are conserved among different plant species and are present in various plastid types.