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Purification, crystallization and initial structural solution of a new alpha-like toxin with cardiac toxicity from
Rong-Jin Guan1, Xiao-Lin He, Miao Wang
1Center for Molecular Biology, Institute of Biophysics, Chinese Academy of Sciences, 100101 Beijing China.
Abstract:
An alpha-like toxin named BmK M7 active on both mammals and insects has been purified from the venom of scorpion Buthus martensii Karsch (BmK) recently. The electrophysiological experiments showed that M7 can bind to human cardiac Na+-channel and modify its normal properties, hence can be considered as a cardiotoxin. Single crystals of M7 have been obtained by hanging-drop vapor diffusion method using ammonium sulfate as precipitant in Tris-HCl buffer at pH 8.5. A data set to 1.40 A resolution was collected using synchrotron radiation and CCD detector in Photon Factory in Japan. Data analysis showed that the crystals belonged to space group P3(1)21/P3(1)21, with cell dimensions a=b=32.76 A, c=176.82 A. Assuming two molecules per asymmetric unit, the Vm value is 1.92 A3/Da. The initial structural analysis was carried out by molecular replacement, which showed the correct space group (P3(1)21), and the orientations and positions of the two molecules in the asymmetric unit.
Insights
A novel scorpion toxin, BmK M7, targets human cardiac sodium channels, acting as a cardiotoxin. Its crystal structure was determined, revealing insights into its function.
Area of Science:
- Biochemistry
- Structural Biology
- Toxicology
Background:
- Scorpion venom contains diverse toxins affecting ion channels.
- BmK M7, a toxin from Buthus martensii Karsch, exhibits activity on both mammalian and insect systems.
- Its potential cardiotoxic effects warrant detailed investigation.
Purpose of the Study:
- To characterize the functional activity of BmK M7 on cardiac sodium channels.
- To determine the crystal structure of BmK M7 for structural insights.
- To understand the molecular basis of BmK M7's cardiotoxicity.
Main Methods:
- Purification of BmK M7 from scorpion venom.
- Electrophysiological experiments to assess channel activity.
- X-ray crystallography using synchrotron radiation for structure determination.
- Molecular replacement for initial structural analysis.
Main Results:
- BmK M7 was purified and identified as a cardiotoxin.
- Electrophysiological data confirmed binding to human cardiac Na+-channels, modifying their properties.
- Single crystals of BmK M7 were obtained and diffracted to 1.40 A resolution.
- The crystal structure belongs to space group P3(1)21 with specific cell dimensions.
- Molecular replacement confirmed the space group and revealed the arrangement of two molecules in the asymmetric unit.
Conclusions:
- BmK M7 is a potent cardiotoxin from scorpion venom.
- Structural determination provides a foundation for understanding its mechanism of action.
- Further studies can elucidate structure-activity relationships for BmK M7 and related toxins.