Atassi M Z, McDaniel C S, Manshouri T
Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030.
J Protein Chem. 1988 Oct;7(5):655-66. doi: 10.1007/BF01024881.
A set of seven peptides constituting the various loops and most of the surface areas of alpha-bungarotoxin (BgTX) was synthesized. In appropriate peptides, the cyclical (by a disulfide bond) monomers were prepared. In all cases, the peptides were purified and characterized. The ability of these peptides to bind Torpedo californica acetylcholine receptor (AChR) was studied by radiometric adsorbent titrations. Three regions, represented by peptides 1-16, 26-41, and 45-59, were able to bind 125I-labeled AChR and, conversely, 125I-labeled peptides were bound by AChR. In these regions, residues Ile-1, Val-2, Trp-28, Lys-26 and/or Lys-38, and one or all of the three residues Ala-45, Ala-46, and Thr-47, are essential contact residues in the binding of BgTX to receptor. Other synthetic regions of BgTX showed little or no AChR-binding activity. The specificity of AChR binding to peptides 1-16, 26-41, and 45-59 was confirmed by inhibition with unlabeled BgTX. It is concluded that BgTX has three main AChR-binding regions (loop I with N-terminal extension and loops II and III extended toward the N-terminal by residues 45-47).
合成了一组由构成α-银环蛇毒素（BgTX）的各种环和大部分表面区域的七个肽段。在合适的肽段中，制备了环状（通过二硫键）单体。在所有情况下，肽段均经过纯化和表征。通过放射性吸附滴定法研究了这些肽段与加州电鳐乙酰胆碱受体（AChR）结合的能力。由肽段1 - 16、26 - 41和45 - 59代表的三个区域能够结合125I标记的AChR，反之，125I标记的肽段也能被AChR结合。在这些区域中，异亮氨酸-1、缬氨酸-2、色氨酸-28、赖氨酸-26和/或赖氨酸-38以及三个残基丙氨酸-45、丙氨酸-46和苏氨酸-47中的一个或全部，是BgTX与受体结合时的关键接触残基。BgTX的其他合成区域显示出很少或没有AChR结合活性。未标记的BgTX抑制作用证实了AChR与肽段1 - 16、26 - 41和45 - 59结合的特异性。得出的结论是，BgTX有三个主要的AChR结合区域（带有N端延伸的环I以及通过残基45 - 47向N端延伸的环II和环III）。
