Sturgess E A, Ballantine J E, Woodland H R, Mohun P R, Lane C D, Dimitriadis G J
J Embryol Exp Morphol. 1980 Aug;58:303-20.
Cytoskeletal beta and gamma-actin are amongst the most rapidly made proteins of oocytes, blastulae and late embryonic stages of Xenopus laevis but, relative to other proteins, the rate of synthesis is low in the egg or cleaving embryo, although the messenger RNA is present in comparable amounts at the different stages. Actin synthesis therefore involves post-transcriptional regulation. alpha-Actin, the actin class characteristics of straited muscle cells, is first detectable in late gastrulae and it is an abundant newly synthetized protein from the neurula stage onwards. mRNA template activity for this protein is not detectable before the gastrula stage. Thus alpha-actin synthesis probably reflects new gene action, confined to part of the embryo, for alpha-actin only appears in the section which includes presumptive skeletal muscle cells. It therefore constitutes the earliest cyto-specific protein so far demonstrated in Amphibia. When tadpole tail poly(A)-containing mRNA is injected into oocytes and eggs alpha-actin synthesis is seen in both cases. Extensive evidence for the identification of the actins is presented. This is based on location of synthesis, DNase-I binding and partial peptide mapping.
细胞骨架β-肌动蛋白和γ-肌动蛋白是非洲爪蟾卵母细胞、囊胚和胚胎后期阶段合成速度最快的蛋白质之一。但是，相对于其他蛋白质而言，在卵或分裂期胚胎中，肌动蛋白的合成速率较低，尽管在不同阶段信使核糖核酸（mRNA）的含量相当。因此，肌动蛋白的合成涉及转录后调控。α-肌动蛋白是横纹肌细胞特有的肌动蛋白类型，最早在原肠胚后期被检测到，从神经胚阶段开始它就是一种大量新合成的蛋白质。在原肠胚阶段之前，无法检测到该蛋白质的mRNA模板活性。因此，α-肌动蛋白的合成可能反映了仅限于胚胎部分区域的新基因作用，因为α-肌动蛋白仅出现在包含推定骨骼肌细胞的部分区域。所以，它是迄今为止在两栖动物中所证明的最早的细胞特异性蛋白质。当将含有多聚腺苷酸（poly(A)）的蝌蚪尾巴mRNA注射到卵母细胞和卵中时，在这两种情况下都能观察到α-肌动蛋白的合成。文中给出了大量用于鉴定肌动蛋白的证据。这是基于合成位置、脱氧核糖核酸酶I（DNase-I）结合以及部分肽图谱分析得出的。
