cd03115

The signal recognition particle (SRP) mediates the transport to or across the plasma membrane in bacteria and the endoplasmic reticulum in eukaryotes. SRP recognizes N-terminal sighnal sequences of newly synthesized polypeptides at the ribosome. The SRP-polypeptide complex is then targeted to the membrane by an interaction between SRP and its cognated receptor (SR). In mammals, SRP consists of six protein subunits and a 7SL RNA. One of these subunits is a 54 kd protein (SRP54), which is a GTP-binding protein that interacts with the signal sequence when it emerges from the ribosome. SRP54 is a multidomain protein that consists of an N-terminal domain, followed by a central G (GTPase) domain and a C-terminal M domain.