Journal Article

pH Sensitivity of the GTPase Toc33 as a Regulatory Circuit for Protein Translocation into Chloroplasts

Tihana Bionda, Patrick Koenig, Mislav Oreb, Ivo Tews and Enrico Schleiff

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 12, pages 1917-1921
Published in print December 2008 | ISSN: 0032-0781
Published online December 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn171
pH Sensitivity of the GTPase Toc33 as a Regulatory Circuit for Protein Translocation into Chloroplasts

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The properties of membrane-embedded GTPases are investigated to understand translocation of preprotein across the outer envelope of chloroplasts. The homo- and heterodimerization events of the GTPases had been established previously. We show that the hydrolytic activity of the GTPase Toc33 is pH insensitive in the homodimeric conformation but has a bell-shaped pH optimum in the monomeric conformation. Further, Toc33 GTPase homodimerization and protein translocation into chloroplasts are pH sensitive as well. pH sensitivity might serve to regulate translocation; alternatively, the documented pH sensitivity might reflect a mechanistic requirement for GTPase silencing during translocation as the GTPase switches between homo- and heterodimeric conformations.

Keywords: Arabidopsis thaliana and Pisum sativum; Dimerization; GTPase; pH sensitivity; Protein translocation; TOC

Journal Article.  2428 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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