Pj. Tranel et K. Keegstra, A NOVEL, BIPARTITE TRANSIT PEPTIDE TARGETS OEP75 TO THE OUTER-MEMBRANE OF THE CHLOROPLASTIC ENVELOPE, The Plant cell, 8(11), 1996, pp. 2093-2104
OEP75 is an outer envelope membrane component of the chloroplastic pro
tein import apparatus and is synthesized in the cytoplasm as a higher
molecular weight precursor (prOEP75). During its own import, prOEP75 i
s processed first to an intermediate (iOEP75) and subsequently to the
mature form (mOEP75). Experiments conducted with stromal extracts indi
cated that iOEP75 was generated from prOEP75 by the activity of the st
romal processing peptidase. The specific processing site was determine
d and used to divide the prOEP75 transit peptide into N- and C-termina
l domains. To determine the targeting functions of the two domains of
the transit peptide and of the mature region of prOEP75, we created a
deletion mutant construct from prOEP75 and chimeric constructs between
domains of prOEP75 and the precursor to a small subunit of ribulose-1
,5-bisphosphate carboxylase/oxygenase. Analysis of these constructs by
in vitro chloroplastic protein import assays revealed that the transi
t peptide of prOEP75 is bipartite in that the N- and C-terminal portio
ns contain chloroplastic and intraorganellar targeting information, re
spectively.