Binds specifically and irreversibly to an allosteric site of the muscarinic acetylcholine M1 receptor (CHRM1) at subnanomolar concentrations and shows a very slow dissociation rate (PubMed:11562434, PubMed:10799315, PubMed:12488533, PubMed:21557730). It also inhibits agonist-mediated guanosine 5'-O-(3'-thiotriphosphate) (GTP-g-S) binding and downstream signaling, and decreases the dissociation rate of orthosteric antagonists (N-methylscopolamine (NMS) or pirenzepine) (PubMed:10799315, PubMed:15033377). Is a potent negative allosteric modulator (NAM) for CHRM1 activation and a positive allosteric modulator (PAM) for antagonist binding (Probable). Expressed by the venom gland. The finger loop 2 blocks access to the orthosteric site of the muscarinic acetylcholine M1 receptor. Comparison of MT7 alone and MT7 in complex with CHRM1 shows that finger loops 1 and 3 undergo large structural rearrangements upon binding to CHRM1, facilitating extensive interactions with the receptor, while finger loop 2 is mostly unchanged. Does not show interaction with adrenergic receptors (ADRA1A, ADRA1B, ADRA1D, ADRA2A, ADRA2B, ADRA2C, ADRB1, ADRB2), dopaminergic receptors (DRD1, DRD2, DRD3, DRD4, DRD5), histaminic receptors (HRH1, HRH3, HRH4) and serotoninergic receptors (HTR1A, HTR2A, HTR2B, HTR2C, HTR5A, HTR6, HTR7) (PubMed:21557730, PubMed:24793485). Does not show interaction with muscarinic receptors (CHRM2, CHRM3, CHRM4, CHRM5) (PubMed:12488533, PubMed:24793485). Is classified as a P-type cytotoxin, since a proline residue stands at position 54 (Pro-31 in standard classification). Belongs to the snake three-finger toxin family. Short-chain subfamily. Aminergic toxin sub-subfamily.