New Structural Motifs Found in Inverterate Proteins.

由于无脊椎动物的多样性，许多新的结构和功能有望在无脊椎动物蛋白质中发现。特别是，无脊椎动物的防御系统，所谓的先天免疫，包括血淋巴凝固和酚氧化酶介导的黑化是由外来物质诱导的，这导致入侵微生物的吞噬。这些固定的入侵者最终被主要从各种血细胞释放的抗菌物质杀死。尽管免疫球蛋白本身的情况下，无脊椎动物的血淋巴是能够响应与高度的特异性对入侵者。本文主要研究了无脊椎动物鲎和线虫中新的防御分子。鲎素是从中国鲎血细胞中分离得到的一种抗菌蛋白。解析的结构由五个二硫键稳定，涉及三链反平行β折叠。发现N-和C-末端是柔性的，没有规则的二级结构。与已知几丁质结合蛋白的结构比较表明，tachycitin的40-60位残基的结构与植物几丁质结合蛋白的结构相似，同时也是从中国鲎（Tachypleus tridentatus）血细胞中分离的一种抗菌蛋白。NOESY光谱分析和结构计算表明，tachystatinA二级结构的主要成分是其分类为+2x，-1的三链β折叠，为主要结构基序。其三维结构与漏斗网蜘蛛毒中的钙通道阻断剂ω-agatoxin IVA相似。猪抗细菌因子）是在猪蛔虫（Ascaris suum）线虫的体液中发现的抗微生物蛋白。ASABF的二级结构由一个α-螺旋和一个β-折叠组成，类似于昆虫防御素的基序。

Many new structures and functions are expected to be found in invertebrate proteins because of the diversity of invertebrate animals. In particular, invertebrate defense systems, so-called innate immunity, include hemolymph coagulation and phenoloxidase-mediated melanization are induced by foreign substances, that result in the engulfment of invading microorganisms. These immobilized invaders are finally killed by antimicrobial substances released mainly from various hemocytes. In spite of the absence of immunoglobulin itself, the invertebrate hemolymph is capable of responding with a high degree of specificity against invaders. The authors focused on the new defense molecules in the invertebrate animals, horseshoe crab and nematode.Tachycitin is an antimicrobial protein isolated from hemocytes of horseshoe crab, Tachypleus tridentatus. The solved structure is stabilized by five disulfide bridges, involving a three stranded antiparallel β-sheet. It is found that the N- and C-terminal are flexible and without regular secondary structures. Structural comparison between tachycitin and the known chitin-binding proteins reveals that the local structure (residues 40-60) of tachycitin is similar to that of plant chitin-binding proteins.Tchystatin is also an antimicrobial protein isolated from hemocytes of horseshoe crab, Tachypleus tridentatus. From NOESY spectra analyses and structure calculations, the main element of secondary structure of tachystatin A is its triple- stranded β-sheet of classificaton +2x, -1 as its dominant structural motif. The three-dimensional structure of tachystatin A is similar with that of calcium channel blocker ω-agatoxin IVA found in venom of funnel web spider.ASABF (A. suum antibacterial factor) is an antimicrobial protein found in the body fluid of the nematode Ascaris suum. The secondary structure of ASABF is composed of one α-helix and one β-sheet like as the motif of insect defensin.