Messerli Mark A, Raihan M Jahir, Kobylkevich Brian M, Benson Austin C, Bruening Kristi S, Shribak Michael, Rosenthal Joshua J C, Sohn Joel J
Biol Bull. 2019 Aug;237(1):1-15. doi: 10.1086/704209. Epub 2019 Jul 8.
The pen, or gladius, of the squid is an internalized shell. It serves as a site of attachment for important muscle groups and as a protective barrier for the visceral organs. The pen's durability and flexibility are derived from its unique composition of chitin and protein. We report the characterization of the structure, development, and composition of pens from . The nanofibrils of the polysaccharide β-chitin are arranged in an aligned configuration in only specific regions of the pen. Chitin is secreted early in development, enabling us to characterize the changes in pen morphology prior to hatching. The chitin and proteins are assembled in the shell sac surrounded by fluid that has a significantly different ionic composition from squid plasma. Two groups of proteins are associated with the pen: those on its surface and those embedded within the pen. Only 20 proteins are identified as embedded within the pen. Embedded proteins are classified into six groups, including chitin associated, protease, protease inhibitors, intracellular, extracellular matrix, and those that are unknown. The pen proteins share many conserved domains with proteins from other chitinous structures. We conclude that the pen is one of the least complex, load-bearing, chitin-rich structures currently known and is amenable to further studies to elucidate natural construction mechanisms using chitin and protein.
鱿鱼的笔状结构，即角质颚，是一种内化的壳。它作为重要肌肉群的附着部位，并作为内脏器官的保护屏障。笔状结构的耐久性和柔韧性源于其几丁质和蛋白质的独特组成。我们报告了来自……的笔状结构的结构、发育和组成特征。多糖β-几丁质的纳米纤维仅在笔状结构的特定区域呈排列状配置。几丁质在发育早期分泌，这使我们能够在孵化前表征笔状结构形态的变化。几丁质和蛋白质在被离子组成与鱿鱼血浆显著不同的液体包围的壳囊中组装。有两组蛋白质与笔状结构相关：其表面的蛋白质和嵌入笔状结构内的蛋白质。仅鉴定出20种蛋白质嵌入笔状结构内。嵌入的蛋白质分为六组，包括与几丁质相关的、蛋白酶、蛋白酶抑制剂、细胞内、细胞外基质以及未知的蛋白质。笔状结构的蛋白质与来自其他含几丁质结构的蛋白质有许多保守结构域。我们得出结论，笔状结构是目前已知的最不复杂、承重、富含几丁质的结构之一，适合进一步研究以阐明利用几丁质和蛋白质的天然构建机制。
