Osborne F A, Stovall S R, Baumstark B R
Department of Biology, Georgia State University, Atlanta 30303.
Nucleic Acids Res. 1989 Oct 11;17(19):7671-80. doi: 10.1093/nar/17.19.7671.
The c1 genes of the heteroimmune phages P1 and P7 were sequenced and their products were compared. P7c1 expression was correlated with the translation in vitro of a protein whose predicted molecular weight (33,000 daltons) is indistinguishable from that of the P1c1 repressor. The c1 regions from both P1 and P7 were found to contain open reading frames capable of coding for a 283-amino acid protein whose predicted secondary structure lacks the helix-turn-helix motif commonly associated with repressor proteins. Two P1c1 amber mutations were localized to the 283-amino acid open reading frame. The P1c1 and P7c1 sequences were found to differ at only 18 positions, all but two of which alter the third position of the affected codon and do not alter the amino acid sequence of the protein. Plasmids expressing the c1 gene from either phage cause the repression of transcription from a cloned promoter situated upstream of P1c1.
对异源免疫噬菌体P1和P7的c1基因进行了测序，并比较了它们的产物。P7 c1的表达与一种预测分子量（33,000道尔顿）与P1 c1阻遏蛋白无法区分的蛋白质的体外翻译相关。发现来自P1和P7的c1区域都含有能够编码一种283个氨基酸的蛋白质的开放阅读框，其预测的二级结构缺乏通常与阻遏蛋白相关的螺旋-转角-螺旋基序。两个P1 c1琥珀突变定位于283个氨基酸的开放阅读框。发现P1 c1和P7 c1序列仅在18个位置不同，其中除两个位置外，所有位置都改变了受影响密码子的第三位，而不改变蛋白质的氨基酸序列。表达来自任一噬菌体的c1基因的质粒导致位于P1 c1上游的克隆启动子的转录受到抑制。
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