Protein SRP68 of human signal recognition particle: identification of the RNA and SRP72 binding domains.

The signal recognition particle (SRP) plays an important role in the delivery of secretory proteins to cellular membranes. Mammalian SRP is composed of six polypeptides among which SRP68 and SRP72 form a heterodimer that has been notoriously difficult to investigate. Human SRP68 was purified from overexpressing Escherichia coli cells and was found to bind to recombinant SRP72 as well as in vitro-transcribed human SRP RNA.