Determinants of Homodimerization Specificity in Histidine Kinases

• Main Authors: Ashenberg, Orr (Contributor), Rozen-Gagnon, Kathryn (Author), Keating, Amy E. (Contributor), Laub, Michael T (Author)
• Other Authors: Massachusetts Institute of Technology. Computational and Systems Biology Program (Contributor), Massachusetts Institute of Technology. Department of Biology (Contributor), Laub, Michael T. (Contributor)
• Format: Article
• Language: English
• Published: Elsevier, 2015-10-02T17:24:18Z.
• Subjects: Article
• Online Access: Get fulltext

Two-component signal transduction pathways consisting of a histidine kinase and a response regulator are used by prokaryotes to respond to diverse environmental and intracellular stimuli. Most species encode numerous paralogous histidine kinases that exhibit significant structural similarity. Yet in almost all known examples, histidine kinases are thought to function as homodimers. We investigated the molecular basis of dimerization specificity, focusing on the model histidine kinase EnvZ and RstB, its closest paralog in Escherichia coli. Direct binding studies showed that the cytoplasmic domains of these proteins each form specific homodimers in vitro. Using a series of chimeric proteins, we identified specificity determinants at the base of the four-helix bundle in the dimerization and histidine phosphotransfer domain. Guided by molecular coevolution predictions and EnvZ structural information, we identified sets of residues in this region that are sufficient to establish homospecificity. Mutating these residues in EnvZ to the corresponding residues in RstB produced a functional kinase that preferentially homodimerized over interacting with EnvZ. EnvZ and RstB likely diverged following gene duplication to yield two homodimers that cannot heterodimerize, and the mutants we identified represent possible evolutionary intermediates in this process.
National Institutes of Health (U.S.) (Award GM067681)
National Science Foundation (U.S.) (CAREER Grant)
National Science Foundation (U.S.). Graduate Research Fellowship