S-adenosyl-L-methionine-binding protein that acts as an inhibitor of mTORC1 signaling via interaction with the GATOR1 and KICSTOR complexes (PubMed:29123071). Acts as a sensor of S-adenosyl-L-methionine to signal methionine sufficiency to mTORC1: in presence of methionine, binds S-adenosyl-L-methionine, leading to disrupt interaction with the GATOR1 and KICSTOR complexes and promote mTORC1 signaling (PubMed:29123071). Upon methionine starvation, S-adenosyl-L-methionine levels are reduced, thereby promoting the association with GATOR1 and KICSTOR, leading to inhibit mTORC1 signaling (PubMed:29123071). Probably also acts as a S-adenosyl-L-methionine-dependent methyltransferase (Potential). Interacts with the GATOR1 complex; interaction is disrupted when BMT2/SAMTOR binds S-adenosyl-L-methionine (PubMed:29123071). Interacts with the KICSTOR complex; interaction is disrupted when BMT2/SAMTOR binds S-adenosyl-L-methionine (PubMed:29123071). Belongs to the BMT2 family.