Shen X, Belcher A M, Hansma P K, Stucky G D, Morse D E
Molecular, Cellular and Developmental Biology Department, University of California, Santa Barbara, California 93106, USA.
J Biol Chem. 1997 Dec 19;272(51):32472-81. doi: 10.1074/jbc.272.51.32472.
A specialized extracellular matrix of proteins and polysaccharides controls the morphology and packing of calcium carbonate crystals and becomes occluded within the mineralized composite during formation of the molluscan shell and pearl. We have cloned and characterized the cDNA coding for Lustrin A, a newly described matrix protein from the nacreous layer of the shell and pearl produced by the abalone, Haliotis rufescens, a marine gastropod mollusc. The full-length cDNA is 4,439 base pairs (bp) long and contains an open reading frame coding for 1,428 amino acids. The deduced amino acid sequence reveals a highly modular structure with a high proportion of Ser (16%), Pro (14%), Gly (13%), and Cys (9%). The protein contains ten highly conserved cysteine-rich domains interspersed by eight proline-rich domains; a glycine- and serine-rich domain lies between the two cysteine-rich domains nearest the C terminus, and these are followed by a basic domain and a C-terminal domain that is highly similar to known protease inhibitors. The glycine- and serine-rich domain and at least one of the proline-rich domains show sequence similarity to proteins of two extracellular matrix superfamilies (one of which also is involved in the mineralized matrixes of bone, dentin, and avian eggshell). The arrangement of alternating cysteine-rich domains and proline-rich domains is strikingly similar to that found in frustulins, the proteins that are integral to the silicified cell wall of diatoms. Its modular structure suggests that Lustrin A is a multifunctional protein, whereas the occurrence of related sequences suggest it is a member of a multiprotein family.
一种由蛋白质和多糖构成的特殊细胞外基质控制着碳酸钙晶体的形态和堆积，并在软体动物贝壳和珍珠形成过程中被包裹在矿化复合物内。我们克隆并鉴定了编码Lustrin A的cDNA，Lustrin A是一种新描述的基质蛋白，来自海洋腹足纲软体动物红鲍（Haliotis rufescens）所产贝壳和珍珠的珍珠层。全长cDNA长4439个碱基对（bp），包含一个编码1428个氨基酸的开放阅读框。推导的氨基酸序列显示出高度模块化的结构，其中Ser（16%）、Pro（14%）、Gly（13%）和Cys（9%）的比例很高。该蛋白包含十个高度保守的富含半胱氨酸的结构域，其间散布着八个富含脯氨酸的结构域；在最靠近C端的两个富含半胱氨酸的结构域之间有一个富含甘氨酸和丝氨酸的结构域，随后是一个碱性结构域和一个与已知蛋白酶抑制剂高度相似的C端结构域。富含甘氨酸和丝氨酸的结构域以及至少一个富含脯氨酸的结构域与两个细胞外基质超家族的蛋白质具有序列相似性（其中一个超家族也参与骨、牙本质和禽蛋壳的矿化基质）。富含半胱氨酸的结构域和富含脯氨酸的结构域交替排列的方式与硅藻硅化细胞壁中不可或缺的蛋白质frustulins中的排列方式惊人地相似。其模块化结构表明Lustrin A是一种多功能蛋白，而相关序列的存在表明它是一个多蛋白家族的成员。
