1. Heterodimeric GTPase core of the SRP targeting complex.
- Author
-
Focia PJ, Shepotinovskaya IV, Seidler JA, and Freymann DM
- Subjects
- Amino Acid Motifs, Bacterial Proteins metabolism, Binding Sites, Catalysis, Crystallography, X-Ray, Dimerization, Guanosine Triphosphate metabolism, Heterotrimeric GTP-Binding Proteins metabolism, Hydrogen Bonding, Hydrophobic and Hydrophilic Interactions, Models, Molecular, Protein Conformation, Protein Structure, Secondary, Protein Structure, Tertiary, Protein Subunits, Receptors, Cytoplasmic and Nuclear metabolism, Signal Recognition Particle metabolism, Bacterial Proteins chemistry, Guanosine Triphosphate analogs & derivatives, Heterotrimeric GTP-Binding Proteins chemistry, Receptors, Cytoplasmic and Nuclear chemistry, Signal Recognition Particle chemistry, Thermus chemistry
- Abstract
Two structurally homologous guanosine triphosphatase (GTPase) domains interact directly during signal recognition particle (SRP)-mediated cotranslational targeting of proteins to the membrane. The 2.05 angstrom structure of a complex of the NG GTPase domains of Ffh and FtsY reveals a remarkably symmetric heterodimer sequestering a composite active site that contains two bound nucleotides. The structure explains the coordinate activation of the two GTPases. Conformational changes coupled to formation of their extensive interface may function allosterically to signal formation of the targeting complex to the signal-sequence binding site and the translocon. We propose that the complex represents a molecular "latch" and that its disengagement is regulated by completion of assembly of the GTPase active site.
- Published
- 2004
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