期刊
TOXICON
卷 38, 期 2, 页码 187-198出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S0041-0101(99)00141-5
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The venom of the green mamba, Dendroaspis angusticeps, was found to have at least six trace m1-specific toxins that block the binding of H-3-N-methylscopolamine to cloned mi muscarinic receptors. Four were isolated by gel filtration, cation exchange HPLC and reversed-phase HPLC and named m1-toxins1-4. Recovery:was 180, 90, 20 and 10 mu g/g dry venom, respectively. m1-Toxin1 (the original ml-toxin) was found to have the sequence, L T C V K S N S I W F P T S E D C P D G Q N L C F R W Q Y I S P R M Y D F T R G C A A T C P K A E Y R D V I N C C G T D K C N K, calculated mass = 7473 Da and calculated pI = 8.2. This sequence had been predicted previously from a cDNA cloned from the venom glands of this snake. The binding of m1-toxin1 was irreversible, so its K-d could not be determined, m1-Toxin2 differed only in proline-19, mass = 7455 and pI = 8.5. Partial sequence data for m1-toxin3 showed aspartate-7 and m1-toxin4 showed isoleucine-12, asparagine-16 and alanine-19. m1-Toxins1-4 have seven conserved amino acids not found in homologous mamba toxins that bind to other muscarinic receptors (MT1, MT2, m4-toxin = MT3, MT4, MT5, MT alpha and MT beta). Some of these residues may be essential for m1-specificity. Since m1-toxin1 binds irreversibly in artificial cerebrospinal fluid at 37 degrees C, it is a particularly attractive antagonist for studies in vivo. (C) 1999 Elsevier Science Ltd. All rights reserved.
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