标题：The lac Repressor Protein: Molecular Shape, Subunit Structure, and Proposed Model for Operator Interaction Based on Structural Studies of Microcrystals
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：1974
卷号：71
期号：3
页码：593-597
DOI：10.1073/pnas.71.3.593
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Electron microscopic and powder x-ray diffraction studies of small crystals of the lac repressor protein provide evidence on its molecular shape and subunit structure which in turn suggests a possible mode of repressor--operator interaction. The crystals are probably orthorhombic space group P2221 with unit cell dimensions of a = 140, b = 91, c = 117 A. This tetrameric protein appears rather asymmetric, having approximate molecular dimensions of 140 A by 60 A by 45 A. The dumbbell shape of the projected molecular outline observed in the electron micrographs can be explained by assuming that the subunits are related by 222 symmetry and are placed at the corners of a plane rectangle. We propose a model for repressor--operator interaction in which the DNA binds to the repressor with its long axis aligned with that of the repressor and with its 2-fold axis coincident with a twofold axis of the repressor.
