Mitcham J L, Prescott D M
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309-0347.
Gene. 1994 Jun 24;144(1):119-22. doi: 10.1016/0378-1119(94)90214-3.
The macronucleus of the hypotrichous ciliate Oxytricha nova contains two DNA molecules with sizes of approx. 1.4 (actin II) and approx. 1.6 (actin I) kb that encode actin (Act) proteins. The 1.6-kb molecule has been previously described [Greslin et al., DNA 7 (1988) 529-536]. The 1.4-kb molecule is described here. The cloned molecule is 1393 bp in length, including 20 bp of telomere sequence at each end. It has an open reading frame (ORF) of 1119 bp that encodes a putative polypeptide of 374 amino acids (aa) designated as ActII. No introns are present. The coding segment is preceded at its 5' end by an A + T-rich 5' noncoding segment of 100 bp, excluding the telomere, and is followed by an A + T-rich 3' noncoding segment of 124 bp, also excluding the telomere. The aa sequence of the actII gene is 63% identical to actI of O. nova and 68, 70 and 69% identical to the rabbit, yeast and Tetrahymena Act aa sequences, respectively. ActI in O. nova is 64 to 68% identical to Act in other eukaryotes. Thus, the two Act in O. nova differ substantially from one another and neither conforms to the conserved Act sequence generally present in eukaryotes.
腹毛目纤毛虫新奥xytricha的大核含有两个DNA分子，大小分别约为1.4（肌动蛋白II）和1.6（肌动蛋白I）kb，它们编码肌动蛋白（Act）蛋白。1.6 kb的分子先前已有描述[Greslin等人，DNA 7 (1988) 529 - 536]。这里描述的是1.4 kb的分子。克隆的分子长度为1393 bp，两端各包含20 bp的端粒序列。它有一个1119 bp的开放阅读框（ORF），编码一个推定的由374个氨基酸（aa）组成的多肽，命名为ActII。不存在内含子。编码区在其5'端之前有一个100 bp的富含A + T的5'非编码区（不包括端粒），之后是一个124 bp的富含A + T的3'非编码区（也不包括端粒）。actII基因的氨基酸序列与新奥xytricha的actI有63%的同一性，与兔、酵母和嗜热四膜虫的肌动蛋白氨基酸序列分别有68%、70%和69%的同一性。新奥xytricha中的ActI与其他真核生物中的肌动蛋白有64%至68%的同一性。因此，新奥xytricha中的两种肌动蛋白彼此差异很大，且均不符合真核生物中普遍存在的保守肌动蛋白序列。
