Graciet, Emmanuelle and Gans, Pierre and Wedel, Norbert and Lebreton, Sandrine and Camadro, Jean-Michel and Gontero, Brigitte (2003) The Small Protein CP12: A Protein Linker for Supramolecular Complex Assembly. Biochemistry, 42 (27). pp. 8163-8170. ISSN 0006-2960

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Abstract

CP12 is an 8.5-kDa nuclear-encoded chloroplast protein, isolated from higher plants. It forms part of a core complex of two dimers of phosphoribulokinase (PRK), two tetramers of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and CP12. The role of CP12 in this complex assembly has not been determined. To address this question, we cloned a cDNA encoding the mature CP12 from the green alga Chlamydomonas reinhardtii and expressed it in Escherichia coli. Sequence alignments show that it is very similar to other CP12s, with four conserved cysteine residues forming two disulfide bridges in the oxidized CP12. On the basis of reconstitution assays and surface plasmon resonance binding studies, we show that oxidized, but not reduced, CP12 acts as a linker in the assembly of the complex, and we propose a model in which CP12 associates with GAPDH, causing its conformation to change. This GAPDH/ CP12 complex binds PRK to form a half-complex (one unit). This unit probably dimerizes due partially to interactions between the enzymes of each unit. Reduced CP12 being unable to reconstitute the complex, we studied the structures of oxidized and reduced CP12 by NMR and circular dichroism to determine whether reduction induced structural transitions. Oxidized CP12 is mainly composed of R helix and coil segments, and is extremely flexible, while reduced CP12 is mainly unstructured. Remarkably, CP12 has similar physicochemical properties to those of “intrinsically unstructured proteins” that are also involved in regulating macromolecular complexes, or in their assembly. CP12s are thus one of the few protein families of intrinsically unstructured proteins specific to plants.

Item Type:	Article
Keywords:	Small Protein CP12; Protein Linker; Supramolecular Complex Assembly;
Academic Unit:	Faculty of Science and Engineering > Biology
Item ID:	7436
Identification Number:	https://doi.org/10.1021/bi034474x
Depositing User:	Emanuelle Graciet
Date Deposited:	08 Sep 2016 15:47
Journal or Publication Title:	Biochemistry
Publisher:	American Chemical Society
Refereed:	Yes
URI:	http://pubs.acs.org
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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