pH sensitivity of the GTPase Toc33 as a regulatory circuit for protein translocation into chloroplasts.
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.
Bionda
Tihana
T
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.
Koenig
Patrick
P
Oreb
Mislav
M
Tews
Ivo
I
Schleiff
Enrico
E
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
D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D011498:Protein Precursors; C114786:Toc33 protein, Arabidopsis; D020558:GTP Phosphohydrolases