3bb4 is a 1 chain structure with sequence from Arabidopsis thaliana. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
TOC33_ARATH GTPase involved in protein precursor import into chloroplasts. Seems to recognize chloroplast-destined precursor proteins and regulate their presentation to the translocation channel through GTP hydrolysis. Binds GTP, GDP, XTP, but not ATP. Probably specialized in the import of nuclear encoded photosynthetic preproteins from the cytoplasm to the chloroplast, especially during early development stages.[1][2][3][4][5][6][7][8][9][10]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
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.
The GTPase cycle of the chloroplast import receptors Toc33/Toc34: implications from monomeric and dimeric structures.,Koenig P, Oreb M, Hofle A, Kaltofen S, Rippe K, Sinning I, Schleiff E, Tews I Structure. 2008 Apr;16(4):585-96. PMID:18400179[11]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
↑Yu TS, Li H. Chloroplast protein translocon components atToc159 and atToc33 are not essential for chloroplast biogenesis in guard cells and root cells. Plant Physiol. 2001 Sep;127(1):90-6. PMID:11553737
↑Aronsson H, Combe J, Jarvis P. Unusual nucleotide-binding properties of the chloroplast protein import receptor, atToc33. FEBS Lett. 2003 Jun 5;544(1-3):79-85. PMID:12782294
↑Weibel P, Hiltbrunner A, Brand L, Kessler F. Dimerization of Toc-GTPases at the chloroplast protein import machinery. J Biol Chem. 2003 Sep 26;278(39):37321-9. Epub 2003 Jul 16. PMID:12869544 doi:https://dx.doi.org/10.1074/jbc.M305946200
↑Wallas TR, Smith MD, Sanchez-Nieto S, Schnell DJ. The roles of toc34 and toc75 in targeting the toc159 preprotein receptor to chloroplasts. J Biol Chem. 2003 Nov 7;278(45):44289-97. Epub 2003 Sep 1. PMID:12951325 doi:https://dx.doi.org/10.1074/jbc.M307873200
↑Kubis S, Baldwin A, Patel R, Razzaq A, Dupree P, Lilley K, Kurth J, Leister D, Jarvis P. The Arabidopsis ppi1 mutant is specifically defective in the expression, chloroplast import, and accumulation of photosynthetic proteins. Plant Cell. 2003 Aug;15(8):1859-71. PMID:12897258
↑Constan D, Patel R, Keegstra K, Jarvis P. An outer envelope membrane component of the plastid protein import apparatus plays an essential role in Arabidopsis. Plant J. 2004 Apr;38(1):93-106. PMID:15053763 doi:https://dx.doi.org/10.1111/j.1365-313X.2004.02024.x
↑Aronsson H, Combe J, Patel R, Jarvis P. In vivo assessment of the significance of phosphorylation of the Arabidopsis chloroplast protein import receptor, atToc33. FEBS Lett. 2006 Jan 23;580(2):649-55. Epub 2005 Dec 28. PMID:16412428 doi:https://dx.doi.org/S0014-5793(05)01538-3
↑Hust B, Gutensohn M. Deletion of core components of the plastid protein import machinery causes differential arrest of embryo development in Arabidopsis thaliana. Plant Biol (Stuttg). 2006 Jan;8(1):18-30. PMID:16435266 doi:https://dx.doi.org/10.1055/s-2005-873044
↑Oreb M, Zoryan M, Vojta A, Maier UG, Eichacker LA, Schleiff E. Phospho-mimicry mutant of atToc33 affects early development of Arabidopsis thaliana. FEBS Lett. 2007 Dec 22;581(30):5945-51. Epub 2007 Dec 3. PMID:18054337 doi:https://dx.doi.org/S0014-5793(07)01225-2
↑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. 2008 Apr;16(4):585-96. PMID:18400179 doi:10.1016/j.str.2008.01.008
