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：2004
卷号：101
期号：32
页码：11646-11651
DOI：10.1073/pnas.0401038101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Although interfaces mediating protein-protein interactions are thought to be under strong evolutionary constraints, binding of the chemotaxis histidine kinase CheA to its phosphorylation target CheY suggests otherwise. The structure of Thermotoga maritima CheA domain P2 in complex with CheY reveals a different association than that observed for the same Escherichia coli proteins. Similar regions of CheY bind CheA P2 in the two systems, but the CheA P2 domains differ by an {approx}90{degrees} rotation. CheA binds CheY with identical affinity in T. maritima and E. coli at the vastly different temperatures where the respective organisms live. Distinct sets of P2 residues mediate CheY binding in the two complexes; conservation patterns of these residues in CheA and compensations in CheY delineate two families of prokaryotic chemotaxis systems. A protein complex that has the same components and general function in different organisms, but an altered structure, indicates unanticipated complexity in the evolution of protein-protein interactions and cautions against extrapolating structural data from homologs.
