UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology

Publication Date


Document Type



Animals; Dogs; Endoplasmic Reticulum; GTP Phosphohydrolases; Proteins; Receptors, Cytoplasmic and Nuclear; Receptors, Peptide; Ribosomes; Signal Recognition Particle


Biochemistry | Biochemistry, Biophysics, and Structural Biology | Molecular Biology | Pharmacology


We have analyzed the interactions between the signal recognition particle (SRP), the SRP receptor (SR), and the ribosome using GTPase assays, biosensor experiments, and ribosome binding assays. Possible mechanisms that could contribute to an enhanced affinity between the SR and the SRP-ribosome nascent chain complex to promote protein translocation under physiological ionic strength conditions have been explored. Ribosomes or 60S large ribosomal subunits activate the GTPase cycle of SRP54 and SRalpha by providing a platform for assembly of the SRP-SR complex. Biosensor experiments revealed high-affinity, saturable binding of ribosomes or large ribosomal subunits to the SR. Remarkably, the SR has a 100-fold higher affinity for the ribosome than for SRP. Proteoliposomes that contain the SR bind nontranslating ribosomes with an affinity comparable to that shown by the Sec61 complex. An NH2-terminal 319-residue segment of SRalpha is necessary and sufficient for binding of SR to the ribosome. We propose that the ribosome-SR interaction accelerates targeting of the ribosome nascent chain complex to the RER, while the SRP-SR interaction is crucial for maintaining the fidelity of the targeting reaction.

DOI of Published Version



J Cell Biol. 2003 Aug 18;162(4):575-85. Epub 2003 Aug 11. Link to article on publisher's site

Journal/Book/Conference Title

The Journal of cell biology

Related Resources

Link to Article in PubMed

PubMed ID