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：2002
卷号：99
期号：4
页码：1831-1835
DOI：10.1073/pnas.032464699
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Anti-sigma factors regulate prokaryotic gene expression through interactions with specific sigma factors. The bacteriophage T4 anti-sigma factor AsiA is a molecular switch that both inhibits transcription from bacterial promoters and phage early promoters and promotes transcription at phage middle promoters through its interaction with the primary sigma factor of Escherichia coli, {sigma}70. AsiA is an all-helical, symmetric dimer in solution. The solution structure of the AsiA dimer reveals a novel helical fold for the protomer. Furthermore, the AsiA protomer, surprisingly, contains a helix-turn-helix DNA binding motif, predicting a potential new role for AsiA. The AsiA dimer interface includes a substantial hydrophobic component, and results of hydrogen/deuterium exchange studies suggest that the dimer interface is the most stable region of the AsiA dimer. In addition, the residues that form the dimer interface are those that are involved in binding to {sigma}70. The results promote a model whereby the AsiA dimer maintains the active hydrophobic surfaces and delivers them to {sigma}70, where an AsiA protomer is displaced from the dimer via the interaction of {sigma}70 with the same residues in AsiA that constitute the dimer interface.
