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57 a.a.
14 a.a.
Key reference
DOI no: 10.1016/j.jmb.2008.05.065 J Mol Biol 381:49-60 (2008) PubMed id: 18586266
Assembly of chloroplast signal recognition particle involves structural rearrangement in cpSRP43. K.M.Kathir, D.Rajalingam, V.Sivaraja, A.Kight, R.L.Goforth, C.Yu, R.Henry, T.K.Kumar. ABSTRACT
Signal recognition particle in chloroplasts (cpSRP) exhibits the unusual ability to bind and target full-length proteins to the thylakoid membrane. Unlike cytosolic SRPs in prokaryotes and eukaryotes, cpSRP lacks an RNA moiety and functions as a heterodimer composed of a conserved 54-kDa guanosine triphosphatase (cpSRP54) and a unique 43-kDa subunit (cpSRP43). Assembly of the cpSRP heterodimer is a prerequisite for post-translational targeting activities and takes place through interactions between chromatin modifier domain 2 (CD2) of cpSRP43 and a unique 10-amino-acid region in cpSRP54 (cpSRP54(pep)). We have used multidimensional NMR spectroscopy and other biophysical methods to examine the assembly and structure of the cpSRP43-cpSRP54 interface. Our data show that CD2 of cpSRP43 binds to cpSRP54(pep) in a 1:1 stoichiometry with an apparent K(d) of approximately 1.06 muM. Steady-state fluorescence and far-UV circular dichroism data suggest that the CD2-cpSRP54(pep) interaction causes significant conformational changes in both CD2 and the peptide. Comparison of the three-dimensional solution structures of CD2 alone and in complex with cpSRP54(pep) shows that significant structural changes are induced in CD2 in order to establish a binding interface contributed mostly by residues in the N-terminal segment of CD2 (Phe5-Val10) and an arginine doublet (Arg536 and Arg537) in the cpSRP54 peptide. Taken together, our results provide new insights into the mechanism of cpSRP assembly and the structural forces that stabilize the functionally critical cpSRP43-cpSRP54 interaction.
Selected figure(s)
Figure 1.
Fig. 1. Amino acid sequence of (a) cpSRP54[pep] and (b) CD2.Figure 5.
Fig. 5. MOLMOL representation of the ensemble of structures of (a) CD2 and (b) CD2 binary complex of CD2 and cpSRP54[pep]. The beta sheets, C-terminal helix, unstructured portions in CD2 and the cpSRP54[pep] are shown in, red, green, blue and gold, respectively. (c and d) Orientation of the C-terminal helix in CD2 (a) and the cpSRP54[pep]–CD2 complex (b). The C-terminal helix in CD2 is oriented at an angle of 62° to the plane of the triple-stranded beta sheet. (c and d) depict the orientation of the C-terminal helix changes by about 40° in the structure of the cpSRP54[pep] complex. (e and f) show the comparison of the hydrogen bonds involving residues in loop IV in CD2 (e) and the cpSRP54[pep]–CD2 complex (f). Binding of cpSRP54[pep] results in the disruption of hydrogen bonds involving residues in loop IV, resulting in a shift in the orientation of the C-terminal helix.The above figures are reprinted from an Open Access publication published by Elsevier: J Mol Biol (2008, 381, 49-60) copyright 2008. Figures were selected by the author.
Literature references that cite this PDB file's key reference
PubMed id Reference
19874542 E.Laugier, L.Tarrago, C.V.Dos Santos, F.Eymery, M.Havaux, and P.Rey (2010).
Arabidopsis thaliana plastidial methionine sulfoxide reductases B, MSRBs, account for most leaf peptide MSR activity and are essential for growth under environmental constraints through a role in the preservation of photosystem antennae.Plant J, 61, 271-282.
19187234 C.Aldridge, P.Cain, and C.Robinson (2009).
Protein transport in organelles: Protein transport into and across the thylakoid membrane.FEBS J, 276, 1177-1186. The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time.
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