Chloroplasts Can Accommodate Inclusion Bodies
EVIDENCE FROM A MUTANT OF CHLAMYDOMONAS REINHARDTII DEFECTIVE IN THE ASSEMBLY OF THE CHLOROPLAST ATP SYNTHASE (*)
- Susan L. Ketchner(1)(§),
- Dominique Drapier(1),
- Jacqueline Olive(2),
- Sophie Gaudriault(1),
- Jacqueline Girard-Bascou(1) and
- Francis-André Wollman(1)(¶)
- From the (1) Service de Photosynthèse, URA/CNRS 1187, Institut de Biologie Physico-Chimique, Paris, France and the
- (2)Laboratoire de Microscopie Electronique, Institut CNRS Jacques Monod, Université Paris VII, Paris France
- ¶ To whom correspondence should be addressed: Service de Photosynthèse, Institut de Biologie Physico-chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France. Tel.: 33-1-43-25-26-09; Fax: 33-1-40-46-83-31; E-mail: Wollman{at}citi2.fr.
Abstract
We identified two neighboring missense mutations in the chloroplast atpA gene which are responsible for the defect of ATP synthase assembly in the FUD16 mutant from Chlamydomonas reinhardtii. The two corresponding amino acid substitutions, Ile
Asn and Asn
Tyr, occurred at strictly conserved sites among the α and β subunits of (C)F1 complexes from bacteria, mitochondria, and chloroplasts. The altered region in the α polypeptide chain is located 7 amino
acids downstream of the P-loop, which forms most of the conserved nucleotide binding site. Although the resulting chloroplast
mutant fails to accumulate most of the ATP synthase subunits, it displays an increased intracellular content in both the α
and β subunits. We demonstrate that the two subunits do not bind to the thylakoid membranes but associate and overaccumulate
in the chloroplast stroma as inclusion bodies. Increased rates of synthesis of the two subunits in the mutant point to an
early interaction between the two subunits during their biogenesis.
Footnotes
-
↵* This work was supported in part by the CNRS/URA 1187 and Human Capital and Mobility network European Economic Community contract ERB CHRX CT 920045. S. L. K. and D. D. contributed equally to the work. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- WT
-
wild-type
- LHC
-
light harvesting complex
- TAP
-
Tris acetate-phosphate
- PAGE
-
polyacrylamide gel electrophoresis.
