An essential role of a TatC homologue of a Delta pH-dependent protein transporter in thylakoid membrane formation during chloroplast development in Arabidopsis thaliana
R. Motohashi et al., An essential role of a TatC homologue of a Delta pH-dependent protein transporter in thylakoid membrane formation during chloroplast development in Arabidopsis thaliana, P NAS US, 98(18), 2001, pp. 10499-10504
Citations number
44
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
At least three transport systems function in targeting nuclear-encoded chlo
roplast proteins to the chloroplast thylakoid membrane. one of these system
s requires a thylakoid pH gradient and is named the Delta pH-dependent prot
ein transport system. A similar Delta pH export system of Escherichia coli
contains four components, twin arginine translocation A (TatA), TatB, TatC,
and TatE. TatC is a major component of the Delta pH-dependent protein tran
sporter in E. coli and functions In the translocation of tightly folded pro
teins across membranes. We have isolated four transposon-inserted albino mu
tants named albino and pale green 2 (apg2) from Arabidopsis thaliana and sh
owed that the transposons were inserted into different sites of a single ge
ne. The APG2 gene product(named cpTatC) has sequence similarity with bacter
ial TatC and contains six putative transmembrane domains, including bacteri
al TatC proteins and a transit peptide in its N terminus. apg2 mutants show
ed albino phenotypes and could not grow in soil. The apg2 plastids were hig
hly vacuolated, lacked internal membrane structures and lamellae of the thy
lakoid membrane, and contained many densely stained globule structures, lik
e undifferentiated proplastids. Immunoblot analysis detected no thylakoid m
embrane proteins such as D1, light-harvesting complex, and OE23 in apg2 pla
stids, whereas soluble proteins such as rubisco large and small subunits we
re not decreased. These results indicate an essential role of cpTatC in chl
oroplast development, especially in thylakoid membrane formation.