The signal recognition particle

The signal recognition particle (SRP) and its membrane-associated receptor (SR) catalyze targeting of nascent secretory and membrane proteins to the p rotein translocation apparatus of the cell. Components of the SRP pathway a nd salient features of the molecular mechanism of SRP-dependent protein tar geting are conserved in all three kingdoms of life. Recent advances in the structure determination of a number of key components in the eukaryotic and prokaryotic SRP pathway provide new insight into the molecular basis of SR P function, and they set the stage for future work toward an integrated pic ture that takes into account the dynamic and contextual properties of this remarkable cellular machine.