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Binding of chloroplast signal recognition particle to a thylakoid membrane protein substrate in aqueous solution and delineation of the cpSRP43–substrate interaction domain

Cain, Peter, Holdermann, Iris, Sinning, Irmgard, Johnson, Arthur E., Robinson, Colin (2011) Binding of chloroplast signal recognition particle to a thylakoid membrane protein substrate in aqueous solution and delineation of the cpSRP43–substrate interaction domain. Biochemical Journal, 437 (1). pp. 149-155. ISSN 0264-6021. (doi:10.1042/BJ20110270) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Official URL
http://dx.doi.org/10.1042/BJ20110270

Abstract

A cpSRP [chloroplast SRP (signal recognition particle)] comprising cpSRP54 and cpSRP43 subunits mediates the insertion of light-harvesting proteins into the thylakoid membrane. We dissected its interaction with a full-length membrane protein substrate in aqueous solution by insertion of site-specific photo-activatable cross-linkers into in vitro-synthesized Lhcb1 (major light-harvesting chlorophyll-binding protein of photosystem II). We show that Lhcb1 residues 166–176 cross-link specifically to the cpSRP43 subunit. Some cross-link positions within Lhcb1 are in the ‘L18’ peptide required for targeting of cpSRP substrates, whereas other cross-linking positions define a new targeting signal in the third transmembrane span. Lhcb1 was not found to cross-link to cpSRP54 at any position, and cross-linking to cpSRP43 is unaffected by the absence of cpSRP54. cpSRP43 thus effectively binds substrates autonomously, and its ability to independently bind an extended 20+-residue substrate region highlights a major difference with other SRP types where the SRP54 subunit binds to hydrophobic target sequences. The results also show that cpSRP43 can bind to a hydrophobic, three-membrane span, substrate in aqueous solution, presumably reflecting a role for cpSRP in the chloroplast stroma. This mode of action, and the specificity of the cpSRP43–substrate interaction, may be associated with cpSRP's unique post-translational mode of action.

Item Type: Article
DOI/Identification number: 10.1042/BJ20110270
Uncontrolled keywords: chloroplast, light-harvesting chlorophyll-binding protein (LHCP), major light-harvesting chlorophyll-binding protein of photosystem II (Lhcb1), photosystem II, signal recognition particle (SRP), thylakoid membrane.
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculties > Sciences > School of Biosciences
Depositing User: Colin Robinson
Date Deposited: 24 Jul 2013 15:38 UTC
Last Modified: 29 May 2019 10:26 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/34847 (The current URI for this page, for reference purposes)
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