Temple M D, Hinds M G, Sheumack D D, Howden M E, Norton R S
School of Biochemistry and Molecular Genetics, University of New South Wales, Sydney, Australia.
Toxicon. 1999 Mar;37(3):485-506. doi: 10.1016/s0041-0101(98)00186-x.
Robustoxin, the lethal neurotoxin from the Sydney funnel web spider Atrax robustus, is a polypeptide of 42 residues cross-linked by four disulfide bonds. This paper describes the sequence-specific assignment of resonances in the 1H nuclear magnetic resonance spectrum of robustoxin in aqueous solution. Several broad backbone amide resonances were encountered in spectra recorded at 27 degrees C, making the assignments at that temperature incomplete. In spectra recorded at lower temperatures these amide resonances became sharper, but others that were sharp at 27 degrees C became broad, indicative of conformational averaging on the millisecond timescale for certain regions of the structure. Nevertheless, it was possible to establish that robustoxin contains a small, triple-stranded, antiparallel beta-sheet and several reverse turns, but no alpha-helix. These observations indicate that this toxin may adopt the inhibitor cystine knot structure found in polypeptides from a diverse range of species, including a number of spiders. Analysis of the pH dependence of the spectrum yielded pKa values for Tyr22 and Tyr25, one of the three carboxyl groups, and the Lys residues.
强劲毒素是悉尼漏斗网蜘蛛（Atrax robustus）产生的致命神经毒素，是一种由42个残基组成的多肽，通过四个二硫键交联。本文描述了在水溶液中强劲毒素的1H核磁共振谱中共振的序列特异性归属。在27摄氏度记录的谱图中遇到了几个宽的主链酰胺共振峰，使得该温度下的归属不完整。在较低温度下记录的谱图中，这些酰胺共振峰变得更尖锐，但在27摄氏度时尖锐的其他共振峰变宽，这表明结构的某些区域在毫秒时间尺度上存在构象平均化。然而，能够确定强劲毒素含有一个小的、三股反平行β折叠和几个反向转角，但没有α螺旋。这些观察结果表明，这种毒素可能采用了在多种物种（包括许多蜘蛛）的多肽中发现的抑制剂胱氨酸结结构。对谱图pH依赖性的分析得出了Tyr22和Tyr25、三个羧基之一以及赖氨酸残基的pKa值。
