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：1973
卷号：70
期号：5
页码：1531-1535
DOI：10.1073/pnas.70.5.1531
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Short DNA duplexes are protected when {lambda} DNA is digested with nuclease in the presence of {lambda} repressor. As the ratio of repressor to operator is increased, six successively larger fragments are recovered, ranging in size from 35 to 100 base pairs, each of which binds repressor. Study of these fragments indicates that, at each of the two {lambda} operators (oL and oR), repressor first binds to a unique site (not necessarily terminal), and that five additional sites are then filled in linear right-ward or left-ward order. The nucleotide sequences and affinities for repressor of oL and oR are not identical, although six fragments of similar size are protected at each operator. Evidence is presented arguing against the existence of hairpin-like structures in the operator fragments, and, moreover, it is shown that the operator duplex does not unwind when repressor binds to it.
