3BB3

Crystal structure of Toc33 from Arabidopsis thaliana in complex with GDP and Mg2+

Summary for 3BB3

• Entry DOI: 10.2210/pdb3bb3/pdb
• Related: 3BB1 3BB4
• Descriptor: T7I23.11 protein, MAGNESIUM ION, GUANOSINE-5'-DIPHOSPHATE, ... (4 entities in total)
• Functional Keywords: rossmann fold, gtpase domain, chloroplast import, gtp-binding, hydrolase, membrane, nucleotide-binding, outer membrane, protein transport, transmembrane, transport
• Biological source: Arabidopsis thaliana (thale cress)
• Cellular location: Plastid, chloroplast outer membrane ; Single- pass membrane protein : O23680
• Total number of polymer chains: 1
• Total formula weight: 29682.99

Authors

Koenig, P.,Sinning, I.,Schleiff, E.,Tews, I. (deposition date: 2007-11-09, release date: 2008-04-01, Last modification date: 2023-11-01)

Primary citation

Koenig, P.,Oreb, M.,Hofle, A.,Kaltofen, S.,Rippe, K.,Sinning, I.,Schleiff, E.,Tews, I.
The GTPase cycle of the chloroplast import receptors Toc33/Toc34: implications from monomeric and dimeric structures.
Structure, 16:585-596, 2008

PubMed Abstract: Transport of precursor proteins across chloroplast membranes involves the GTPases Toc33/34 and Toc159 at the outer chloroplast envelope. The small GTPase Toc33/34 can homodimerize, but the regulation of this interaction has remained elusive. We show that dimerization is independent of nucleotide loading state, based on crystal structures of dimeric Pisum sativum Toc34 and monomeric Arabidopsis thaliana Toc33. An arginine residue is--in the dimer--positioned to resemble a GAP arginine finger. However, GTPase activation by dimerization is sparse and active site features do not explain catalysis, suggesting that the homodimer requires an additional factor as coGAP. Access to the catalytic center and an unusual switch I movement in the dimeric structure support this finding. Potential binding sites for interactions within the Toc translocon or with precursor proteins can be derived from the structures.

PubMed: 18400179
DOI: 10.1016/j.str.2008.01.008

Experimental method

X-RAY DIFFRACTION (2.94 Å)