Import Of Proteins Into Chloroplasts

JORGELINA OTTADO; CECCARELLI, EDUARDO; NÉSTOR CARRILLO

Recent Research Development in Plant Physiology

Año: 1997 vol. 1 p. 145 - 152

Most plastid proteins are nuclear-encoded, synthesized in cytosolic polysomes as higher molecular mass precursors, and then translocated into the stroma, from which they are subsequently routed to the various compartments and membrane systems within the organelle. Though the mechanism of chloroplast protein import has been investigated extensively, it is not yet completely understood. In the last few years, however, the development of various systems for the expression in microorganisms of plant precursors and mature proteins opened new opportunities to investigate the molecular mechanism(s) underlying protein import into plastids. Recent progresses include: 1) the quantitative estimation of binding parameters and protein import kinetics using in vitro systems of defined composition; 2) the characterization of many polypeptides belonging to translocation complexes; and 3) insights into the conformation of transport-competent precursors. These developments, sustained by the systematic use of purified recombinant precursor proteins in in vitro import experiments with isolated chloroplasts, are likely to provide the impetus for more detailed mechanistic studies of protein transport across the plastid membrane.