Sabareesh V, Gowd K Hanumae, Ramasamy P, Sudarslal S, Krishnan K S, Sikdar S K, Balaram P
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
Peptides. 2006 Nov;27(11):2647-54. doi: 10.1016/j.peptides.2006.07.009. Epub 2006 Sep 1.
Distinctly different effects of two closely related contryphans have been demonstrated on voltage-activated Ca(2+) channels. The peptides Lo959 and Am975 were isolated from Conus loroisii, a vermivorous marine snail and Conus amadis, a molluscivore, respectively. The sequences of Lo959 and Am975 were deduced by mass spectrometric sequencing (MALDI-MS/MS) and confirmed by chemical synthesis. The sequences of Lo959, GCP(D)WDPWC-NH(2) and Am975, GCO(D)WDPWC-NH(2) (O: 4-trans-hydroxyproline: Hyp), differ only at residue 3; Pro in Lo959, Hyp in Am975, which is identical to contryphan-P, previously isolated from Conus purpurascens, a piscivore; while Lo959 is a novel peptide. Both Lo959 and Am975 undergo slow conformational interconversion under reverse-phase chromatographic conditions, a characteristic feature of all contryphans reported thus far. Electrophysiological studies performed using dorsal root ganglion neurons reveal that both peptides target high voltage-activated Ca(2+) channels. While Lo959 increases the Ca(2+) current, Am975 causes inhibition. The results establish that subtle sequence effects, which accompany post-translational modifications in Conus peptides, can have dramatic effects on target ion channels.
已证实两种密切相关的芋螺毒素对电压激活的Ca(2+)通道具有截然不同的作用。肽Lo959和Am975分别从食虫海洋蜗牛Conus loroisii和食软体动物的Conus amadis中分离得到。Lo959和Am975的序列通过质谱测序（基质辅助激光解吸电离串联质谱法，MALDI-MS/MS）推导得出，并通过化学合成得到证实。Lo959的序列为GCP(D)WDPWC-NH(₂)，Am975的序列为GCO(D)WDPWC-NH(₂)（O：4-反式羟基脯氨酸：Hyp），仅在第3位残基不同；Lo959中的脯氨酸，Am975中的Hyp，这与之前从食鱼的Conus purpurascens中分离得到的芋螺毒素-P相同；而Lo959是一种新型肽。在反相色谱条件下，Lo959和Am975都会发生缓慢的构象互变，这是迄今为止报道的所有芋螺毒素的一个特征。使用背根神经节神经元进行的电生理研究表明，这两种肽都作用于高电压激活的Ca(2+)通道。虽然Lo959增加Ca(2+)电流，但Am975则导致抑制。结果表明，芋螺肽翻译后修饰伴随的细微序列效应可对靶离子通道产生显著影响。
