The structure of Escherichia coli signal recognition particle revealed by scanning transmission electron microscopy.
Structural studies on various domains of the ribonucleoprotein signal recognition particle (SRP) have not converged on a single complete structure of bacterial SRP consistent with the biochemistry of the particle. We obtained a three-dimensional structure for Escherichia coli SRP by cryoscanning transmission electron microscopy and mapped the internal RNA by electron spectroscopic imaging. Crystallographic data were fit into the SRP reconstruction, and although the resulting model differed from previous models, they could be rationalized by movement through an interdomain linker of Ffh, the protein component of SRP. Fluorescence resonance energy transfer experiments determined interdomain distances that were consistent with our model of SRP. Docking our model onto the bacterial ribosome suggests a mechanism for signal recognition involving interdomain movement of Ffh into and out of the nascent chain exit site and suggests how SRP could interact and/or compete with the ribosome-bound chaperone, trigger factor, for a nascent chain during translation.
Mainprize
Iain L
IL
Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton L8N 3Z5, Canada.
Beniac
Daniel R
DR
Falkovskaia
Elena
E
Cleverley
Robert M
RM
Gierasch
Lila M
LM
Ottensmeyer
F Peter
FP
Andrews
David W
DW
D004926:Escherichia coli / Q000648:ultrastructure*; D031541:Fluorescence Resonance Energy Transfer; D017348:Microscopy, Electron, Scanning Transmission / Q000379:methods*; D046032:Microscopy, Energy-Filtering Transmission Electron; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D012329:RNA, Bacterial / Q000737:chemistry; D012270:Ribosomes / Q000378:metabolism; D018271:Signal Recognition Particle / Q000648:ultrastructure*; D012996:Solutions
D021122:Protein Subunits; D012329:RNA, Bacterial; D018271:Signal Recognition Particle; D012996:Solutions