Characterization of D-amino-acid-containing excitatory conotoxins and redefinition of the I-conotoxin superfamily
Characterization of D-amino-acid-containing excitatory conotoxins and redefinition of the I-conotoxin superfamily
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DOI：
10.1111/j.1742-4658.2005.04830.x
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发表时间：
2005-08-01
期刊：
影响因子：
5.4
通讯作者：
Olivera, BM
中科院分区：
文献类型：
--
作者：
Buczek, O;Yoshikami, D;Olivera, BM
L-氨基酸翻译后异构化为D-氨基酸是一种微妙的修饰，不能通过标准技术如Edman测序或MS检测到。准确的预测需要更多的修饰多肽序列。一个46个氨基酸长的芋螺毒素，r11 a，属于I-超家族，先前显示有一个D-苯丙氨酸残基在位置44。在这份报告中，我们表征两个相关的肽，r11 b和r11 c，与D-苯丙氨酸和D-亮氨酸，分别在同源位置。电生理测试表明，所有三个肽诱导重复活动在青蛙运动神经，和差向异构化的单个氨基酸在第三个位置从C-末端减弱的效力r11 a和r11 b，但不是r11 c。此外，r11 c（r11 a和r11 b都没有）也作用于骨骼肌。我们鉴定了更多编码芋螺肽前体的cDNA克隆，其Cys模式类似于r11 a/B/c。虽然预测的成熟毒素具有相同的半胱氨酸模式，但它们属于两个不同的基因超家族。的基因超家族的身份，其中I-芋螺毒素属于和D-氨基酸的存在或不存在的主要序列之间的潜在相关性进行了讨论。巨大的多样性的I-芋螺肽序列提供了一个难得的机会，定义参数，可能是重要的，这最隐蔽的所有翻译后修饰。我们的研究结果表明，无论是侧链的化学性质，也不是精确的邻位序列周围的修饰残基似乎是至关重要的，但可能有有利的位点异构化为D-氨基酸。
Post-translational isomerization of L-amino acids to D-amino acids is a subtle modification, not detectable by standard techniques such as Edman sequencing or MS. Accurate predictions require more sequences of modified polypeptides. A 46-amino-acid-long conotoxin, r11a, belonging to the I-superfamily was previously shown to have a D-Phe residue at position 44. In this report, we characterize two related peptides, r11b and r11c, with D-Phe and D-Leu, respectively, at the homologous position. Electrophysiological tests show that all three peptides induce repetitive activity in frog motor nerve, and epimerization of the single amino acid at the third position from the C-terminus attenuates the potency of r11a and r11b, but not that of r11c. Furthermore, r11c (but neither r11a nor r11b) also acts on skeletal muscle. We identified more cDNA clones encoding conopeptide precursors with Cys patterns similar to r11a/b/c. Although the predicted mature toxins have the same cysteine patterns, they belong to two different gene superfamilies. A potential correlation between the identity of the gene superfamily to which the I-conotoxin belongs and the presence or absence of a D-amino acid in the primary sequence is discussed. The great diversity of I-conopeptide sequences provides a rare opportunity for defining parameters that may be important for this most stealthy of all post-translational modifications. Our results indicate that neither the chemical nature of the side chain nor the precise vicinal sequence around the modified residue seem to be critical, but there may be favored loci for isomerization to a D-amino acid.