Editor-in-Chief: Brüne, Bernhard
Editorial Board: Buchner, Johannes / Lei, Ming / Ludwig, Stephan / Sies, Helmut / Thomas, Douglas D. / Turk, Boris / Wittinghofer, Alfred
IMPACT FACTOR 2017: 3.022
CiteScore 2017: 2.81
SCImago Journal Rank (SJR) 2017: 1.562
Source Normalized Impact per Paper (SNIP) 2017: 0.705
The Chloroplast Import Receptor Toc34 Functions as Preprotein-Regulated GTPase
Toc34 is a protein of the chloroplast outer envelope membrane that acts as receptor for preproteins containing a transit sequence. The recognition of preproteins by Toc34 is regulated by GTP binding and phosphorylation. The phosphorylation site of Toc34 is located at serine 113, close to the postulated triphosphate binding site. This can explain the downregulation of Toc34 by phosphorylation, resulting in the loss of GTP binding. Vice versa, GTP but not GDP binding of Toc34 influences the phosphorylation. The nucleotide specificity of Toc34 is not only determined by the classical nucleotide binding domains but by a nontypical region at the Nterminus of the protein. As a result, the GTP binding properties are unusual, since the triphosphate moiety of GTP is bound with higher affinity than the purine base. Purified Toc34 hydrolyses GTP at a low rate, which could regulate the receptor function. The rate of hydrolysis is greatly stimulated by a precursor protein.
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