Horse complement protein C9: primary structure and cytotoxic activity.
Horse complement protein C9: primary structure and cytotoxic activity.
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马补体蛋白 C9：一级结构和细胞毒活性。
DOI：
10.1016/0161-5890(96)00007-7
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发表时间：
1996
影响因子：
3.6
通讯作者：
Stanley,KK
中科院分区：
文献类型：
--
作者：
Esser,AF;Tarnuzzer,RW;Tomlinson,S;Tatar,LD;Stanley,KK
马血清缺乏溶血活性是马 C9 的固有特性。为了了解这种缺陷的分子原因，我们从马肝 cDNA 文库中克隆了 C9 cDNA，并对 cDNA 进行了测序，得到了马 C9 的完整编码序列。从马血浆中纯化 C9 并通过微测序确定成熟蛋白的 N 末端，并验证已分离出正确的马 C9 cDNA 克隆。推导的氨基酸序列对应于 526 个氨基酸的成熟蛋白质，与人 C9 具有 77% 的一致性。它具有与人类 C9 相同的结构域，包含 22 个半胱氨酸和 4 个不变的色氨酸。少数差异包括 N 末端，在马 C9 中是未封闭的甘氨酸，但在人 C9 中是焦谷氨酰胺，以及三个潜在的 N-糖基化位点（与人 C9 中的两个相比）。 N 端差异并不重要，因为对具有强溶血性的牛 C9 进行微测序，确定它也具有与马 C9 相同的未封闭的甘氨酸。没有明显的结构差异可以解决两个分子之间溶血效力的差异。除了一些保守的替换之外，两个 C9 序列在位置 250 和 360 之间是相同的。该区域包括 C9 中的膜相互作用结构域和假定的跨膜片段，该跨膜片段被认为构成假定的跨膜孔壁，因此应该是细胞毒性所必需的。与这一预测一致，我们观察到，与溶血活性的显着降低相反，马C9在杀死多种革兰氏阴性细菌方面非常有效。这些结果证明马C9是一种结构上具有有效细胞毒活性的分子。它无法裂解红细胞可能与靶细胞膜上的对照蛋白的作用有关。
Lack of hemolytic activity of horse serum is an inherent property of horse C9. To understand the molecular reasons for this deficiency we have cloned C9 cDNA from a horse liver cDNA library and have sequenced the cDNA yielding the complete coding sequence for horse C9. Purification of C9 from horse plasma and microsequencing established the N-terminus of the mature protein and verified that the correct horse C9 cDNA clone had been isolated. The deduced amino acid sequence corresponds to a mature protein of 526 amino acids that is 77% identical to human C9. It has the same domain structure as human C9 and contains 22 cysteines and four invariant tryptophanes. The few differences include the N-terminus, which is an unblocked glycine in horse C9 but pyroglutamine in human C9, and three potential N-glycosylation sites compared to two in human C9. The N-terminal difference is unimportant since microsequencing of bovine C9, which is strongly hemolytic, established that it also has an unblocked glycine identical to horse C9. There are no obvious structural differences apparent that could resolve the differences in hemolytic potency between the two molecules. Aside from a few conservative replacements, both C9 sequences are identical between positions 250 and 360. This region includes the membrane interaction domain in C9 and the postulated transmembrane segment that is thought to constitute the wall of a putative transmembrane pore and, therefore, should be required for cytotoxicity. In agreement with this prediction we have observed that, in contrast to the marked decrease in hemolytic activity, horse C9 is very efficient in killing a variety of Gram-negative bacteria. These results demonstrate that horse C9 is a structurally competent molecule with efficient cytotoxic activity. Its inability to lyse erythrocytes may be related to the action of control proteins on target cell membranes.
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DOI：
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