Anti-M-1 antibodies are protein reagents that detect specific antigens. The M-1 antigen is another term for the human protein cholinergic receptor muscarinic 1, encoded by the CHRM1 gene. The protein is known to function in chemical synaptic transmission and GPCR signaling pathways, among other biological roles. Canonically, it has an amino acid length of 460 residues and a mass of 51.4 kilodaltons. Its subcellular localization is in the cell membrane and it is expressed in the rectum, hippocampus, cerebral cortex, and cerebellum. The M-1 protein is a member of the G-protein coupled receptor 1 protein family.