Key Laboratory for Marine Living Resources and Molecular Engineering, College of Marine Science, Zhejiang Ocean University, Zhoushan 316000, Zhejiang Province, PR China.
Fish Shellfish Immunol. 2013 Feb;34(2):610-6. doi: 10.1016/j.fsi.2012.11.030. Epub 2012 Dec 14.
Antimicrobial peptides (AMPs) are components of the innate immune responses that form the first line of host defense against pathogens. Marine mussels can produce a surprising abundance of cysteine-rich AMPs pertaining to the defensin, myticin, mytilin and mytimycin families, particularly in the circulating hemocytes. In the current study, we purified and characterized a novel cysteine-rich peptide with remarkable antibacterial activity from Mytilus coruscus and designated with myticusin-1, a 104-amino acid long polypeptide including 10 cysteine residues forming an unusual cysteine pattern. Antimicrobial assays demonstrated that myticusin-1 exhibited stronger anti-microbial properties against Gram-positive bacteria more than Gram-negative bacteria and fungus. Furthermore, myticusin-1 caused significant morphological alterations in both Sarcina luteus and Escherichia coli as shown by transmission electron microscopy (TEM). The cDNA of myticusin-1 was cloned and sequenced from the hemocytes cDNA library of M. coruscus. The mRNA transcripts of myticusin-1 are mainly detected in hemocyte, which indicates that myticusin-1 are specifically synthesized and stored in circulating hemocytes. The expression level of myticusin-1 in hemocytes was up-regulated and reached the highest level at 36 h after S. luteus challenge, which was 20-fold increase compared to that of the control group. These results indicated that myticusin-1 was involved in the host immune response against bacterial infection and might contribute to the clearance of invading bacteria.
抗菌肽（AMPs）是先天免疫反应的组成部分，构成宿主防御病原体的第一道防线。海洋贻贝可以产生丰富的含半胱氨酸的 AMPs，属于防御素、肌肽、肌肽和肌肽霉素家族，特别是在循环血细胞中。在本研究中，我们从贻贝中纯化并鉴定了一种具有显著抗菌活性的新型含半胱氨酸肽，并将其命名为肌肽素-1，这是一种 104 个氨基酸长的多肽，包含 10 个半胱氨酸残基，形成一种不寻常的半胱氨酸模式。抗菌测定表明，肌肽素-1对革兰氏阳性菌的抗菌特性强于革兰氏阴性菌和真菌。此外，肌肽素-1通过透射电子显微镜（TEM）显示，对 Sarcina luteus 和 Escherichia coli 均引起明显的形态改变。从贻贝血细胞 cDNA 文库中克隆并测序了肌肽素-1 的 cDNA。肌肽素-1 的 mRNA 转录本主要在血细胞中检测到，这表明肌肽素-1是特异性合成并储存在循环血细胞中的。在 S. luteus 攻击后 36 小时，血细胞中肌肽素-1的表达水平上调，并达到最高水平，与对照组相比增加了 20 倍。这些结果表明，肌肽素-1参与了宿主对细菌感染的免疫反应，并可能有助于清除入侵的细菌。
