Binding of chloroplast signal recognition particle to a thylakoid membrane protein substrate in aqueous solution and delineation of the cpSRP43-substrate interaction domain
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-specifi...
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| Main Authors: | , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
June 14 2011
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| In: |
Biochemical journal
Year: 2011, Volume: 437, Issue: 1, Pages: 149-155 |
| ISSN: | 1470-8728 |
| DOI: | 10.1042/BJ20110270 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1042/BJ20110270
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| Author Notes: | Peter Cain, Iris Holdermann, Irmgard Sinning, Arthur E. Johnson and Colin Robinson |
| Summary: | 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. |
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| Item Description: | Im Titel ist die Zahl 43 tiefgestellt Gesehen am 27.06.2022 |
| Physical Description: | Online Resource |
| ISSN: | 1470-8728 |
| DOI: | 10.1042/BJ20110270 |