Structural characterization of the major extrapallial fluid protein of the mollusc Mytilus edulis: implications for function.
Structural characterization of the major extrapallial fluid protein of the mollusc Mytilus edulis: implications for function.
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DOI：
10.1021/bi0505565
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发表时间：
2005-08
期刊：
影响因子：
2.9
通讯作者：
Yan Yin;Jing Huang;M. Paine;V. Reinhold;N. Chasteen
中科院分区：
文献类型：
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作者：
Yan Yin;Jing Huang;M. Paine;V. Reinhold;N. Chasteen
软体动物紫贻贝的外套膜液的主要蛋白质组分先前已被分离和部分表征。由于其具有与Ca（2+）结合诱导自组装的有趣特性，推测其在壳矿化中起作用。然而，它也结合其他二价离子，包括Cd（2+）、Cu（2+）、Mn（2+）和Mg（2+）。本文首次报道了通过RT-PCR和cDNA测序方法以及质谱法从头肽序列测定对外膜（EP）蛋白一级结构的表征。EP蛋白由23个氨基酸的信号肽裂解后的213个氨基酸组成。该蛋白质富含His、Glu和Asp残基。还表征了氨基酸位置54-57处的N-糖基化位点“NHTE”以及蛋白质的Cys 139和Cys 171之间的分子内二硫键。序列比较表明，EP蛋白具有很少的同源性，任何目前已知的基质蛋白以前分离的软体动物外壳，而是它非常类似的重金属结合蛋白和富含组氨酸的糖蛋白，都从血淋巴的M。美味。预测的结构域和氨基酸组成表明，其N-末端可能参与钙结合。该蛋白质中组氨酸残基的丰度可能是其重金属结合特性的原因。因此，EP蛋白可能具有多种功能，充当Ca（2+）-转运蛋白、壳基质蛋白和重金属解毒蛋白。
The major protein component of the extrapallial fluid of the mollusc Mytilus edulis has been previously isolated and partially characterized. It was postulated to play a role in shell mineralization because of its intriguing property of Ca(2+)-binding-induced self-assembling. However, it also binds other divalent ions, including Cd(2+), Cu(2+), Mn(2+), and Mg(2+). Herein is the initial report on the characterization of the primary structure of the extrapallial (EP) protein by RT-PCR and cDNA sequencing methods and by de novo peptide sequencing with mass spectrometry. The EP protein is comprised of 213 amino acids postcleavage of a signal peptide of 23 amino acids. The protein is rich in His, Glu, and Asp residues. The site of N-glycosylation, "NHTE", at amino acid positions 54-57 and the intramolecular disulfide bond between Cys 139 and Cys 171 of the protein have been characterized also. Sequence comparisons reveal that the EP protein possesses little homology to any presently known matrix proteins previously isolated from mollusc shells but rather it highly resembles a heavy metal binding protein and a histidine-rich glycoprotein, both from the hemolymph of M. edulis. The predicted domain profile and amino acid composition suggest that its N-terminus may be involved in calcium binding. The abundance of histidine residues of the protein may account for its heavy metal binding properties. Thus, the EP protein perhaps has multiple functions, serving as a Ca(2+)-transport protein, a shell matrix protein, and a heavy metal detoxification protein.