期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：5
页码：2271-2275
DOI：10.1073/pnas.75.5.2271
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Methyl groups placed on {phi}XsB1 replicative form DNA by the Escherichia coli B modification enzyme are located in the overlap between fragments Mbo II-3 and Alu I-2, a 61-base-pair DNA segment. Mutations that led to loss of susceptibility to restriction by E. coli B occurred within this segment at three positions spanning 14 nucleotides. A sequence difference between {phi}XsB1 and {phi}Xam3cs70, a {phi}X174 strain not restricted by E. coli B, occurs at one of these positions. The site on simian virus 40 DNA methylated by the modification enzyme is located in the 115-base-pair overlap between fragments Hae III-I and Alu I-G. The sequences of these segments of {phi}XsB1 and simian virus 40 DNA and two regions of phage f1 DNA recognized by the E. coli B restriction enzyme [Ravetch, J. V., Horiuchi, K. & Zinder, N. D. (1978) Proc. Natl. Acad. Sci. USA 75, 2266-2270] contain a homology of nine bases in the configuration: 5'-T-G-A... 8N... T-G-C-T... 9N... T-N-N-T-3'. The sequence 5'-T-G-A... 8N... T-G-C-T-3' may constitute the restriction enzyme recognition site since it does not occur in {phi}Xam3cs70 DNA and occurs only once in simian virus 40 DNA, and since all observed mutations leading to loss of the site occur at one of the bases specified by this sequence. Analysis of the sequence of {phi}Xam3cs70 showed that if no other residues are recognized, all seven of these bases are essential for recognition and the interval between the two groups of specified bases must be precisely eight.
