Component of the signal recognition particle (SRP) complex receptor (SR) (PubMed:16439358). Ensures, in conjunction with the SRP complex, the correct targeting of the nascent secretory proteins to the endoplasmic reticulum membrane system (PubMed:16675701, PubMed:34020957). Forms a guanosine 5'-triphosphate (GTP)-dependent complex with the SRP subunit SRP54 (PubMed:34020957). SRP receptor compaction and GTPase rearrangement drive SRP-mediated cotranslational protein translocation into the ER (PubMed:34020957). Heterodimer with SRPRB (PubMed:16439358). Interacts with the signal recognition particle (SRP) complex subunit SRP54 (PubMed:34020957). (Microbial infection) May interact with Zika virus strain Mr-766 non-structural protein 4A/NS4A (PubMed:30550790). May interact with Zika virus French Polynesia 10087PF/2013 non-structural protein 4A/NS4A (PubMed:30550790). (Microbial infection) May interact with Dengue virus DENV2 16681 non-structural protein 4A/NS4A. Thought to be anchored in the membrane through an interaction with SR-beta, which contains a bona fide transmembrane domain. The NG domain region, also named G domain, is a special guanosine triphosphatase (GTPase) domain, which forms a guanosine 5'-triphosphate (GTP)-dependent complex with a homologous NG domain in the signal recognition particle (SRP) complex subunit SRP54 (PubMed:34020957). The two NG domains undergo cooperative rearrangements upon their assembly, which culminate in the reciprocal activation of the GTPase activity of one another (PubMed:34020957). GTPase induced rearrangement of SR drives SRP-mediated cotranslational protein translocation into the ER (PubMed:34020957). Belongs to the GTP-binding SRP family.