Elongation arrest is a physiologically important function of signal recognition particle.
Signal recognition particle (SRP) targets proteins for co-translational insertion through or into the endoplasmic reticulum membrane. Mammalian SRP slows nascent chain elongation by the ribosome during targeting in vitro. This 'elongation arrest' activity requires the SRP9/14 subunit of the particle and interactions of the C-terminus of SRP14. We have purified SRP from Saccharomyces cerevisiae and demonstrated that it too has elongation arrest activity. A yeast SRP containing Srp14p truncated at its C-terminus (delta C29) did not maintain elongation arrest, was substantially deficient in promoting translocation and interfered with targeting by wild-type SRP. In vivo, this mutation conferred a constitutive defect in the coupling of protein translation and translocation and temperature-sensitive growth, but only a slight defect in protein translocation. In combination, these data indicate that the primary defect in SRP delta C29 is in elongation arrest, and that this is a physiologically important and conserved function of eukaryotic SRP.
Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, University of Edinburgh, Swann Building, The King's Buildings, Mayfield Road, Edinburgh EH9 3JR, UK.
N
N
Mason
L F
LF
Ciufo
J D
JD
Brown
D001692:Biological Transport; D002451:Cell Compartmentation; D009154:Mutation; D010441:Peptide Chain Elongation, Translational; D016601:RNA-Binding Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D018271:Signal Recognition Particle / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D016601:RNA-Binding Proteins; C089642:SRP14 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D018271:Signal Recognition Particle; C490325:Srp14 protein, mouse; C503637:Srp72 protein, mouse