矛头蝮毒素-I：氨基酸序列与功能。
Bothropstoxin-I: amino acid sequence and function.
作者信息
Cintra A C, Marangoni S, Oliveira B, Giglio J R
机构信息
Departamento de Bioquímica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brasil.
出版信息
J Protein Chem. 1993 Feb;12(1):57-64. doi: 10.1007/BF01024915.
The complete amino acid sequence of bothropstoxin-I (BthTX-I), a myotoxin isolated from Bothrops jararacussu snake venom, is reported. The results show that BthTX-I is a Lys49 phospholipase A2 (PLA2)-like protein composed of a single polypeptide chain of 121 amino acid residues (M(r) = 13,720), containing one methionine and 14 half-cystines. Although deprived of any detectable PLA2 activity, BthTX-I reveals a high degree of sequence homology with Asp49-PLA2s and with other Lys49-myotoxins. Critical mutations--such as Leu5 for Phe5; Gln11 for X11; Asn28 for Tyr28; Leu32 for Gly32; Lys49 for Asp49; and Asp71 for Asn71--which are apparently involved with the decreasing or elimination of PLA2 activity, have been detected. The same mutations occurred in myotoxin II from Bothrops asper venom, but five extra changes--namely, Pro90 for Ser90; Gly111 for Asn111; His120 for Tyr120; Phe124 for Leu124; and Pro132 for Ala132--have been found relative to myotoxin II.
报道了从巴西矛头蝮蛇毒中分离出的一种肌毒素——矛头蝮毒素 -I（BthTX-I）的完整氨基酸序列。结果表明，BthTX-I 是一种 Lys49 磷脂酶 A2（PLA2）样蛋白，由一条 121 个氨基酸残基的单多肽链组成（M(r)=13,720），含有一个甲硫氨酸和 14 个半胱氨酸。尽管缺乏任何可检测到的 PLA2 活性，但 BthTX-I 与 Asp49-PLA2 和其他 Lys49-肌毒素具有高度的序列同源性。已检测到一些关键突变，如 Leu5 突变为 Phe5；Gln11 突变为 X11；Asn28 突变为 Tyr28；Leu32 突变为 Gly32；Lys49 突变为 Asp49；Asp71 突变为 Asn71，这些突变显然与 PLA2 活性的降低或消除有关。在粗鳞矛头蝮蛇毒的肌毒素 II 中也发生了同样的突变，但相对于肌毒素 II 还发现了另外五个变化，即 Pro90 突变为 Ser90；Gly111 突变为 Asn111；His120 突变为 Tyr120；Phe124 突变为 Leu124；Pro132 突变为 Ala132。
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