Jung G, Schmidt C J, Hammer J A
Laboratory of Cell Biology, NHLBI, Bethesda, MD 20892.
Gene. 1989 Oct 30;82(2):269-80. doi: 10.1016/0378-1119(89)90052-8.
We have determined the complete sequence and structure of a second myosin I heavy-chain gene from Acanthamoeba castellanii. This gene, which we have named MIL, spans approx. 6kb, is split by 17 introns, encodes a 1147-aa polypeptide, and is transcribed in log-phase cells. The positions of six of the introns are conserved relative to a vertebrate muscle myosin gene. Similar to the previously characterized MIB heavy-chain gene, the deduced MIL heavy-chain aa sequence reveals a 125-kDa protein composed of a myosin globular head domain joined to a novel, approx. 50-kDa C-terminal domain that is rich in glycine, proline and alanine residues. There are differences, however, between MIL and MIB in the sequence organization of their unconventional C-terminal domains. We conclude from this and other data that Acanthamoeba express at least three myosin I heavy-chain isoforms: MIL, plus MIA and MIB, whose purifications have been published previously. Amoeba genomic DNA blots probed with a short, highly conserved sequence whose position is transposed between MIB and MIL indicate that the Acanthamoeba myosin I heavy-chain gene family may actually contain as many as six genes. Finally, we compared the myosin I sequences with those of two related proteins, Drosophila NinaC and the bovine myosin I-like protein, and found that a portion of the unconventional C-terminal domains of the amoeba myosins I and the bovine protein appear to be related.
我们已经确定了来自卡氏棘阿米巴的第二个肌球蛋白I重链基因的完整序列和结构。这个基因，我们命名为MIL，跨度约6kb，被17个内含子分隔，编码一个1147个氨基酸的多肽，并在对数期细胞中转录。其中六个内含子的位置相对于脊椎动物肌肉肌球蛋白基因是保守的。与之前鉴定的MIB重链基因相似，推导的MIL重链氨基酸序列显示一个125kDa的蛋白质，由一个肌球蛋白球状头部结构域连接到一个新的、约50kDa的富含甘氨酸、脯氨酸和丙氨酸残基的C末端结构域组成。然而，MIL和MIB在其非常规C末端结构域的序列组织上存在差异。我们从这些以及其他数据得出结论，棘阿米巴表达至少三种肌球蛋白I重链异构体：MIL，加上MIA和MIB，它们的纯化方法先前已经发表。用一个短的、高度保守的序列探测变形虫基因组DNA印迹，该序列的位置在MIB和MIL之间发生了转换，这表明棘阿米巴肌球蛋白I重链基因家族实际上可能包含多达六个基因。最后，我们将肌球蛋白I序列与两种相关蛋白质——果蝇NinaC和牛肌球蛋白I样蛋白的序列进行了比较，发现变形虫肌球蛋白I和牛蛋白的非常规C末端结构域的一部分似乎是相关的。
