In different organisms, the mode of interaction between two signaling proteins is not necessarily conserved
Park, S.Y., Beel, B.D., Simon, M.I., Bilwes, A.M., Crane, B.R.(2004) Proc Natl Acad Sci U S A 101: 11646-11651
- PubMed: 15289606 
- DOI: 10.1073/pnas.0401038101
- Primary Citation of Related Structures:  
1U0S - PubMed Abstract: 
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 ...