Sequence-specific 1H-NMR assignment and determination of the secondary structure of hainantoxin-III from the spider Ornithoctonus hainana

Hainantoxin-iii (hntx-iii) purified from the venom of the spider ornithoctonus hainana is a novel neurotoxin preferentially inhibiting tetrodotoxin-sensitive voltage-gated sodium channels in rat dorsal root ganglion cells. the structure of this toxin in aqueous solution was investigated using 2-d 1h-nmr techniques. the complete sequencespecific assignments of proton resonances in the 1h-nmr spectra were obtained by analyzing a series of 2-d spectra,including dqf-cosy,tocsy and noesy spectra,in h 2o or d2o. all the backbone protons and more than 95% of the side-chain protons have been assigned by dαn,d βn,and dnn connectivities in noesy spectrum. furthermore,the secondary structure of hntx-iii was identified from nmr data. it consists mainly of a short triple-stranded antiparallel sheet formed by asp7 to cys9,tyr21 to ser23,and lys27 to val30. because hntx-iii shares high sequence identity (>70%) with hwtx-i and hntx-i,we proposed that they all share a structural scaffold known as the inhibitor cystine knot architectural motif. this study provides a basis for the further determination of the solution conformation of hntx-iii. © 2013 bentham science publishers.