Guanine nucleotide-binding protein that plays a crucial role in the cellular response to amino acid availability through regulation of the mTORC1 signaling cascade (PubMed:20381137, PubMed:27234373, PubMed:24095279). Forms heterodimeric Rag complexes with RRAGA or RRAGB and cycles between an inactive GTP-bound and an active GDP-bound form (PubMed:24095279). In its active form participates in the relocalization of mTORC1 to the lysosomes and its subsequent activation by the GTPase RHEB (PubMed:20381137, PubMed:27234373, PubMed:24095279). This is a crucial step in the activation of the TOR signaling cascade by amino acids (PubMed:20381137, PubMed:27234373, PubMed:24095279). GTP + H2O = GDP + H(+) + phosphate In high-amino acid conditions, activated by GTPase activating protein (GAP) FLCN that stimulates RRAGC GTPase activity to turn it into its active GDP-bound form. Forms a heterodimer with RRAGA, in a sequence-independent manner, and RRAGB (PubMed:11073942, PubMed:14660641). Heterodimerization stabilizes proteins of the heterodimer (PubMed:11073942). In complex with RRAGA or RRAGB, interacts with RPTOR; this interaction is particularly efficient with GTP-loaded RRAGB and GDP-loaded RRAGC (PubMed:18497260). Component of the lysosomal folliculin complex (LFC), composed of FLCN, FNIP1 (or FNIP2), RRAGA/RagA or RRAGB/RagB GDP-bound, RRAGC/RagC or RRAGD/RagD GTP-bound, and Ragulator (PubMed:31704029, PubMed:31672913). Interacts with NOL8 (PubMed:14660641). Interacts with SH3BP4; the interaction with this negative regulator is most probably direct, preferentially occurs with the inactive GDP-bound form of RRAGB, is negatively regulated by amino acids and prevents interaction with RPTOR (PubMed:22575674). The Rag heterodimer interacts with SLC38A9; the probable amino acid sensor (PubMed:25561175, PubMed:25567906). Interacts with SESN1, SESN2 and SESN3 (PubMed:25259925). Interacts with PIP4P1 (By similarity). The GDP-bound form interacts with TFE3 (By similarity). Predominantly cytoplasmic. May shuttle between the cytoplasm and nucleus, depending on the bound nucleotide state of associated RRAGA (PubMed:11073942). RRAGC mutations have been found in a patient with idiopathic dilated cardiomyopathy with ventricular dilation and systolic dysfunction, bilateral cataracts, and mild facial dysmorphisms. Belongs to the GTR/RAG GTP-binding protein family. Truncated N-terminus.