X-ray structure of the T. aquaticus FtsY:GDP complex suggests functional roles for the C-terminal helix of the SRP GTPases |
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Authors: | Gawronski-Salerno Joseph Coon John S Focia Pamela J Freymann Douglas M |
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Institution: | Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, Illinois 60611, USA. |
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Abstract: | FtsY and Ffh are structurally similar prokaryotic Signal Recognition Particle GTPases that play an essential role in the Signal Recognition Particle (SRP)-mediated cotranslational targeting of proteins to the membrane. The two GTPases assemble in a GTP-dependent manner to form a heterodimeric SRP targeting complex. We report here the 2.1 A X-ray structure of FtsY from T. aquaticus bound to GDP. The structure of the monomeric protein reveals, unexpectedly, canonical binding interactions for GDP. A comparison of the structures of the monomeric and complexed FtsY NG GTPase domain suggests that it undergoes a conformational change similar to that of Ffh NG during the assembly of the symmetric heterodimeric complex. However, in contrast to Ffh, in which the C-terminal helix shifts independently of the other subdomains, the C-terminal helix and N domain of T. aquaticus FtsY together behave as a rigid body during assembly, suggesting distinct mechanisms by which the interactions of the NG domain "module" are regulated in the context of the two SRP GTPases. |
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Keywords: | SRP Ffh FtsY SR GTPase GDP X‐ray crystallography |
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