PDBsum entry: 2hug

Plant protein

PDB id: 2hug

Contents

Protein chains

57 a.a.

14 a.a.

PDB id:

2hug

Name:

Plant protein

Title:

3d solution structure of the chromo-2 domain of cpsrp43 complexed with cpsrp54 peptide

Structure:

Signal recognition particle 43 kda protein, chloroplast. Chain: a. Fragment: chromo-2 domain (residues 265-319). Synonym: cpsrp43, chromo protein srp43. Engineered: yes. Signal recognition particle 54 kda protein, chloroplast. Chain: b.

Source:

Arabidopsis thaliana. Thale cress. Organism_taxid: 3702. Gene: cao. Expressed in: escherichia coli. Expression_system_taxid: 562. Expression_system_taxid: 562

NMR struc:

20 models

Authors:

K.M.Kathir,S.Vaithiyalingam,R.Henry,S.K.K.Thallapuranam

Key ref:

K.M.Kathir et al. (2008). Assembly of chloroplast signal recognition particle involves structural rearrangement in cpSRP43. J Mol Biol, 381, 49-60. PubMed id: 18586266 DOI: 10.1016/j.jmb.2008.05.065

Date:

26-Jul-06 Release date: 18-Sep-07

Protein chain

O22265  (SR43C_ARATH) -  Signal recognition particle 43 kDa protein, chloroplastic

Seq: 373 a.a.

Struc: 57 a.a.*

Protein chain

P37107  (SR54C_ARATH) -  Signal recognition particle 54 kDa protein, chloroplastic

Seq: 564 a.a.

Struc: 14 a.a.

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

 Gene Ontology (GO) functional annotation 

• Cellular component: nucleus (2 terms)
• Biological process: chromatin assembly or disassembly (1 term)
• Biochemical function: chromatin binding (1 term)

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.