GTPase domain of signal recognition particle protein
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 signal 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.
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