Baron M D, Davison M D, Jones P, Critchley D R
Department of Biochemistry, University of Leicester, United Kingdom.
J Biol Chem. 1987 Dec 25;262(36):17623-9.
We have sequenced a cDNA, isolated from a chick embryo fibroblast lambda gt11 library, that encodes all 887 amino acids of alpha-actinin. Sequence from 10 different peptides from chick smooth muscle alpha-actinin was found to match that derived from the cDNA. The deduced protein sequence can be divided into three distinct domains: (a) the N-terminal 240 amino acid contains a highly conserved region (compared with Dictyostelium alpha-actinin) which probably represents the actin-binding domain, (b) amino acids 270-740 contain four repeats of a spectrin-like sequence, and (c) the C-terminal sequence contains two EF-hand Ca2+-binding sites. Each of these sites is defective in at least one oxygen-containing Ca2+-chelating amino acid side chain, suggesting that they are nonfunctional. Southern blots suggest that the alpha-actinin cDNA described here hybridizes to only one gene in chicken. Northern blots reveal only one size class of mRNA in fibroblasts and smooth muscle, but no hybridizing species could be detected in skeletal muscle poly(A+) RNA. The results are consistent with the view that smooth and skeletal muscle alpha-actinins are encoded by separate genes, which are considerably divergent.
我们对从鸡胚成纤维细胞λgt11文库中分离得到的一个cDNA进行了测序，该cDNA编码α - 辅肌动蛋白的全部887个氨基酸。发现来自鸡平滑肌α - 辅肌动蛋白的10种不同肽段的序列与从该cDNA推导的序列相匹配。推导的蛋白质序列可分为三个不同的结构域：(a) N端的240个氨基酸包含一个高度保守的区域（与盘基网柄菌α - 辅肌动蛋白相比），可能代表肌动蛋白结合结构域；(b) 270 - 740位氨基酸包含四个血影蛋白样序列重复；(c) C端序列包含两个EF手型Ca²⁺结合位点。这些位点中的每一个在至少一个含氧化钙的Ca²⁺螯合氨基酸侧链上存在缺陷，表明它们无功能。Southern杂交表明，此处描述的α - 辅肌动蛋白cDNA在鸡中仅与一个基因杂交。Northern杂交显示在成纤维细胞和平滑肌中只有一种大小类别的mRNA，但在骨骼肌多聚腺苷酸（poly(A)⁺）RNA中未检测到杂交物种。这些结果与平滑肌和骨骼肌α - 辅肌动蛋白由不同基因编码且差异很大的观点一致。
