Shigenaga T, Muta T, Toh Y, Tokunaga F, Iwanaga S
Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
J Biol Chem. 1990 Dec 5;265(34):21350-4.
The hemocytes of the horseshoe crab have been found to contain a new family of Arthropodous antibiotics, termed the "tachyplesin family." These peptides are composed of 17-18 amino acid residues with a carboxyl-terminal arginine alpha-amide. We report here the entire cDNA sequence coding for the tachyplesin precursors and their distribution in various tissues of the horseshoe crab. Sequence analysis of the cloned cDNAs revealed that the tachyplesin precursors consist of 77 amino acids with 23 residues in a presegment, and that there are two types of mRNAs corresponding to the isopeptides tachyplesins I and II. Both precursors contain a putative signal peptide, a processing peptide sequence and a carboxyl-terminal amidation signal "Gly-Lys-Arg" connected to the mature tachyplesin peptide. Moreover, an unusual acidic amino acid cluster, Asp-Glu-Asp-Glu-Asp-Asp-Asp-Glu-Glu-COOH, is present in the carboxyl-terminal portions of both precursors. These results suggest that the two types of tachyplesin precursors are first synthesized as preproproteins and are then incorporated into the intracellular organelle, accompanied by various processing events. Northern blot analysis on a total RNA from various tissues of the horseshoe crab revealed that the tachyplesin precursors are expressed mainly in hemocytes and cardiac and brain tissues. Tachyplesin was immunohistochemically localized in the smaller dense granules rather than the typical large granules present in abundance in the hemocytes.
鲎的血细胞中发现含有一个新的节肢动物抗生素家族，称为“鲎素家族”。这些肽由17 - 18个氨基酸残基组成，羧基末端为精氨酸α-酰胺。我们在此报告编码鲎素前体的完整cDNA序列及其在鲎不同组织中的分布。对克隆的cDNA进行序列分析表明，鲎素前体由77个氨基酸组成，前肽段有23个残基，并且存在两种对应于异肽鲎素I和II的mRNA。两种前体均包含一个推定的信号肽、一个加工肽序列以及与成熟鲎素肽相连的羧基末端酰胺化信号“Gly-Lys-Arg”。此外，在两种前体的羧基末端部分均存在一个不寻常的酸性氨基酸簇，即Asp-Glu-Asp-Glu-Asp-Asp-Asp-Glu-Glu-COOH。这些结果表明，两种类型的鲎素前体首先作为前原蛋白合成，然后伴随着各种加工事件被整合到细胞内细胞器中。对鲎不同组织的总RNA进行Northern印迹分析表明，鲎素前体主要在血细胞以及心脏和脑组织中表达。通过免疫组织化学方法将鲎素定位在较小的致密颗粒中，而非血细胞中大量存在的典型大颗粒中。
