Nucleotides and Substrates Trigger the Dynamics of the Toc34 GTPase Homodimer Involved in Chloroplast Preprotein Translocation

详细信息    查看全文

• 作者：Christina Lumme¹ ; ⁹ ; ¹⁰ ; Hasret Altan-Martin² ; ⁹ ; Reza Dastvan³ ; ⁵ ; ⁷ ; ⁸ ; ⁹ ; Maik S. Sommer² ; Mislav Oreb¹ ; ¹¹ ; Denise Schuetz³ ; ⁵ ; ⁷ ; Bjö ; rn Hellenkamp¹ ; Oliver Mirus² ; Jens Kretschmer² ; ¹⁴ ; Sevdalina Lyubenova³ ; ⁵ ; ⁷ ; ¹² ; Wolfgang Kü ; gel⁴ ; Jan P. Medelnik² ; ¹³ ; Manuela Dehmer² ; Jens Michaelis⁴ ; Thomas F. Prisner³ ; ⁵ ; ⁷ ; Thorsten Hugel¹ ; Enrico Schleiff² ; ⁵ ; ⁶ ; ^{schleiff@bio.uni-frankfurt.de" class="auth_mail}
• 刊名：Structure
• 出版年：8 April, 2014
• 年：2014
• 卷：22
• 期：4
• 页码：526-538
• 全文大小：3084 K

文摘

| Figures/TablesFigures/Tables | ReferencesReferences

Summary

GTPases are molecular switches that control numerous crucial cellular processes. Unlike bona fide GTPases, which are regulated by intramolecular structural transitions, the less well studied GAD-GTPases are activated by nucleotide-dependent dimerization. A member of this family is the translocase of the outer envelope membrane of chloroplast Toc34 involved in regulation of preprotein import. The GTPase cycle of Toc34 is considered a major circuit of translocation regulation. Contrary to expectations, previous studies yielded only marginal structural changes of dimeric Toc34 in response to different nucleotide loads. Referencing PELDOR and FRET single-molecule and bulk experiments, we describe a nucleotide-dependent transition of the dimer flexibility from a tight GDP- to a flexible GTP-loaded state. Substrate binding induces an opening of the GDP-loaded dimer. Thus, the structural dynamics of bona fide GTPases induced by GTP hydrolysis is replaced by substrate-dependent dimer flexibility, which likely represents a general regulatory mode for dimerizing GTPases.