Specific citrullination causes assembly of a globular S100A3 homotetramer -: A putative Ca2+ modulator matures human hair cuticle
Specific citrullination causes assembly of a globular S100A3 homotetramer -: A putative Ca2+ modulator matures human hair cuticle
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DOI：
10.1074/jbc.m709357200
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发表时间：
2008-02-22
影响因子：
4.8
通讯作者：
Heizmann, Claus W.
中科院分区：
文献类型：
--
作者：
Kizawa, Kenji;Takahara, Hidenari;Heizmann, Claus W.
S100A3是钙离子结合蛋白S100家族中唯一的成员，具有最高的半胱氨酸含量和对锌离子的亲和力。这种蛋白在毛囊内的分化角质层细胞中高度表达，并组织成成熟的毛发角质层。以前的研究表明，S100A3与上皮分化密切相关，导致毛干形成，但其分子功能仍不清楚。通过使用修饰的瓜氨酸抗体进行双向PAGE-Western印迹分析，我们发现天然S100A3的一半以上的精氨酸残基被依赖于钙的肽基精氨酸脱亚胺酶逐步转化为瓜氨酸。免疫荧光共聚焦显微镜显示，角质层内的S100A3与PAD3的III型亚型共定位，但不与PAD1共定位。重组PAD1和PAD2能将重组S100A3中的4种精氨酸全部转化为瓜氨酸，而PAD3只能将Arg-51特异性地转化为瓜氨酸。凝胶过滤分析表明，无论是S100A3中Arg-51的酶促转化为瓜氨酸，还是其与丙氨酸(R51a)的突变替代都促进了同源四聚体的组装。荧光滴定R51a表明，在四聚过程中，其潜在的钙结合性能增强。提出了一个带有瓜氨酸残基的球状钙结合S100A3四聚体的原型结构模型。高浓度的S100A3同源四聚体可能提供形成毛发角质层屏障所需的毫摩尔水平的钙离子。
S100A3 is a unique member of the Ca2+- binding S100 protein family with the highest cysteine content and affinity for Zn2+. This protein is highly expressed in the differentiating cuticular cells within the hair follicle and organized into mature hair cuticles. Previous studies suggest a close association of S100A3 with epithelial differentiation, leading to hair shaft formation, but its molecular function is still unknown. By two-dimensional PAGE-Western blot analyses using a modified citrulline antibody, we discovered that more than half of the arginine residues of native S100A3 are progressively converted to citrullines by Ca2+-dependent peptidylarginine deiminases. Confocal immunofluorescent microscopy showed that the cytoplasmic S100A3 within the cuticular layer is mostly co-localized with the type III isoform of peptidylarginine deiminase (PAD3) but not with PAD1. Recombinant PAD1 and PAD2 are capable of converting all 4 arginines in recombinant S100A3, whereas PAD3 specifically converts only Arg-51 into citrulline. Gel filtration analyses showed that either enzymatic conversion of Arg-51 in S100A3 to citrulline or its mutational substitution with alanine (R51A) promotes a homotetramer assembly. Fluorescent titration of R51A suggested that its potential Ca2+ binding property increased during tetramerization. A prototype structural model of the globular Ca2+- bound S100A3 tetramer with citrulline residues is presented. High concentrations of S100A3 homotetramer might provide the millimolar level of Ca2+ required for hair cuticular barrier formation.