9630775 Krishna The proposed research will focus on the structures and dynamics of long chain neurotoxins isolated from the New World scorpion Centruroides sculpturatus Ewing, and the Old World species Leiurus quinquestriatus quinquestriatus. Specifically, several neurotoxic proteins from both species will be purified and sequenced. The proteins that will be characterized will include both the long chain - and neurotoxins. Standard 2D-NMR methods as well as NOESY-TOCSY will be employed to extract experimental constraints needed for structure refinement calculations. Protein breathing motions will be probed by measuring amide proton exchange life times. The order parameters and correlation times will be measured from 13C relaxation time measurement at natural abundance using a double DEPT sequence. The differences in the structures and dynamical behavior within each class, and between the two classes of proteins will be examined. A number of hypotheses on the structure- function relationships among this class of proteins will be tested. %%% Neurotoxins serve as excellent probes of ion channels Despite a high degree of sequence homology, the scorpion neuroxtoxins can differ dramatically in their toxicities and the nature of interactions with the ion channels. The proposed studies will be important in understanding the intriguing differences exhibited by the - and - toxins. This work will significantly enhance fundamental knowledge on the molecular mechanism of interactions between the neurotoxic proteins and the sodium channel. ***
