Chloroplast transit peptides: structure, function and evolution.
It is thought that two to three thousand different proteins are targeted to the chloroplast, and the 'transit peptides' that act as chloroplast targeting sequences are probably the largest class of targeting sequences in plants. At a primary structural level, transit peptide sequences are highly divergent in length, composition and organization. An emerging concept suggests that transit peptides contain multiple domains that provide either distinct or overlapping functions. These functions include direct interaction with envelope lipids, chloroplast receptors and the stromal processing peptidase. The genomic organization of transit peptides suggests that these domains might have originated from distinct exons, which were shuffled and streamlined throughout evolution to yield a modern, multifunctional transit peptide. Although still poorly characterized, this evolutionary process could yield transit peptides with different domain organizations. The plasticity of transit peptide design is consistent with the diverse biological functions of chloroplast proteins.
Bruce
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BD
Dept of Biochemistry, Cellular and Molecular Biology Department, The Center for Legume Research, University of Tennessee-Knoxville, USA. bbruce@utk.edu
D001692:Biological Transport / Q000502:physiology; D002736:Chloroplasts / Q000378:metabolism*; D019143:Evolution, Molecular; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*
D010940:Plant Proteins; D021382:Protein Sorting Signals