Lucas Jared M, Vaccaro Eleonora, Waite J Herbert
Marine Science Institute and Molecular, Cellular and Developmental, Biology Department, University of California at Santa Barbara, Santa Barbara, CA 93106, USA.
J Exp Biol. 2002 Jun;205(Pt 12):1807-17. doi: 10.1242/jeb.205.12.1807.
Marine mussels are renowned for their ability to produce an extra-organismic tendon-like structure that can withstand the wave forces associated with the intertidal habitat. Initial characterization of byssal properties has focused on Mytilus edulis, with few detailed comparisons with other mussels. M. galloprovincialis, a closely related species, provides an opportunity for a thorough comparison. Three full-length cDNA clones encoding the byssal collagens, precollagen D (preCol-D), preCol-NG and preCol-P, were isolated from M. galloprovincialis. Comparisons with M. edulis preCol-D, preCol-NG and preCol-P reveal a 91.3 %, 88.6 % and 90.1 % identity with the cDNA and an 89.0 %, 88.1 % and 89.0 % identity with the deduced protein sequences, respectively. Key elements are maintained between the species: in particular, modeled bends in the collagen helix due to breaks in the Gly-X-Y pattern and the location of cysteine and putative 3,4-dihydroxyphenylalanine (DOPA) residues. A potentially important difference between the two is that, in all cases, M. galloprovincialis byssal collagens contain additional histidine residues in their flanking domains. The significance of this may lie in the ability of M. galloprovincialis to utilize more metal chelate cross-links, which have been implicated in byssal thread stability. M. edulis threads are typically twice the length and diameter of M. galloprovincialis threads and appear to contain nearly 10 % more collagen. These differences are maintained even when the different thread portions are compared. Despite differences in a number of parameters, most notably that whole M. galloprovincialis threads are stiffer, threads whether whole or separated into proximal and distal portions, have similar mechanical behaviors. It is apparent from this comparison that M. galloprovincialis and M. edulis are seemingly interchangeable models for byssal research.
海洋贻贝以其能够产生一种体外肌腱样结构而闻名，这种结构能够承受与潮间带栖息地相关的波浪力。足丝属性的初步表征主要集中在紫贻贝上，与其他贻贝的详细比较较少。加利福尼亚贻贝是一种亲缘关系密切的物种，为进行全面比较提供了机会。从加利福尼亚贻贝中分离出了三个编码足丝胶原蛋白的全长cDNA克隆，即前胶原蛋白D（preCol-D）、前胶原蛋白NG和前胶原蛋白P。与紫贻贝的preCol-D、preCol-NG和preCol-P进行比较，发现其与cDNA的同一性分别为91.3%、88.6%和90.1%，与推导的蛋白质序列的同一性分别为89.0%、88.1%和89.0%。两个物种之间的关键元素得以保留：特别是，由于甘氨酸-X-酪氨酸模式的中断以及半胱氨酸和假定的3,4-二羟基苯丙氨酸（DOPA）残基的位置，胶原蛋白螺旋中形成的模拟弯曲。两者之间一个潜在的重要差异是，在所有情况下，加利福尼亚贻贝的足丝胶原蛋白在其侧翼结构域中含有额外的组氨酸残基。这一点的重要性可能在于加利福尼亚贻贝利用更多金属螯合交联的能力，并与足丝的稳定性有关。紫贻贝的丝通常是加利福尼亚贻贝丝长度和直径的两倍，并且似乎含有比胶原蛋白多近10%的胶原蛋白。即使比较不同的丝段，这些差异仍然存在。尽管在许多参数上存在差异，最明显的是整个加利福尼亚贻贝的丝更硬，但无论是完整的丝还是分成近端和远端部分的丝，都具有相似的力学行为。从这个比较中可以明显看出，加利福尼亚贻贝和紫贻贝似乎是足丝研究中可互换的模型。
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