title: pH sensitivity of the GTPase Toc33 as a regulatory circuit for protein translocation into chloroplasts.
abstract: 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.
authors.affiliation: JWGU Frankfurt am Main, Cluster of Excellence Macromolecular Complexes, Center of Membrane Proteomics, Department of Biosciences, Molecular Cell Biology, Max-von-Laue Str. 9, D-60439 Frankfurt, Germany.
authors.forename: Tihana
authors.initials: T
authors.lastname: Bionda
authors.forename: Patrick
authors.initials: P
authors.lastname: Koenig
authors.forename: Mislav
authors.initials: M
authors.lastname: Oreb
authors.forename: Ivo
authors.initials: I
authors.lastname: Tews
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D011498:Protein Precursors / Q000378:metabolism; D021381:Protein Transport
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D011498:Protein Precursors; C114786:Toc33 protein, Arabidopsis; D020558:GTP Phosphohydrolases