Anti-HM-1 antibodies enable researchers to detect and measure the HM-1 antigen in biological samples. This target is a reported synonym of the CHRM1 gene, which encodes cholinergic receptor muscarinic 1. This protein is known to function in chemical synaptic transmission and GPCR signaling pathways, among other biological roles. The human version of HM-1 has a canonical amino acid length of 460 residues and a protein mass of 51.4 kilodaltons, although 2 isoforms have been identified. It is reported to be localized in the cell membrane of cells and notably expressed in the rectum, hippocampus, cerebral cortex, and cerebellum. HM-1 is a member of the G-protein coupled receptor 1 protein family.