Subunit exchange by CheA histidine kinases from the mesophile Escherichia coli and the thermophile Thermotoga maritima.
Dimerization of the chemotaxis histidine kinase CheA is required for intersubunit autophosphorylation [Swanson, R. V., Bourret, R. B., and Simon, M. I. (1993) Mol. Microbiol. 8, 435-441]. Here we show that CheA dimers exchange subunits by the rate-limiting dissociation of a central four-helix bundle association domain (P3), despite the high stability of P3 versus unfolding. P3 alone determines the stability and exchange properties of the CheA dimer. For CheA proteins from the mesophile Escherichia coli and the thermophile Thermotoga maritima, subunit dissociation activates at temperatures where the respective organisms live (37 and 80 degrees C). Under destabilizing conditions, P3 dimer dissociation is cooperative with unfolding. Chemical denaturation is reversible for both EP3 and TP3. Aggregation accompanies thermal unfolding for both proteins under most conditions, but thermal unfolding is reversible and two-state for EP3 at low protein concentrations. Residue differences within interhelical loops may account for the contrasted thermodynamic properties of structurally similar EP3 and TP3 (41% sequence identity). Under stabilizing conditions, greater correlation between activation energy for dimer dissociation and P3 stability suggests more unfolding in the dissociation of EP3 than TP3. Furthermore, destabilization of extended conformations by glycerol slows relative dissociation rates more for EP3 than for TP3. Nevertheless, at physiological temperatures, neither protein likely unfolds completely during subunit exchange. EP3 and TP3 will not exchange subunits with each other. The receptor coupling protein CheW reduces the subunit dissociation rate of the T. maritima CheA dimer by interacting with the regulatory domain P5.
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
Sang-Youn
SY
Park
Cindy M
CM
Quezada
Alexandrine M
AM
Bilwes
Brian R
BR
Crane
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D002633:Chemotaxis; D019281:Dimerization; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D000071677:Histidine Kinase; D007700:Kinetics; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D000072236:Methyl-Accepting Chemotaxis Proteins; D008956:Models, Chemical; D008969:Molecular Sequence Data; D017510:Protein Folding; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D040681:Structural Homology, Protein; D013696:Temperature; D013816:Thermodynamics; D020124:Thermotoga maritima / Q000201:enzymology* / Q000254:growth & development
D001426:Bacterial Proteins; C489103:CheW protein, E coli; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D047428:Protein Kinase Inhibitors; D021122:Protein Subunits; C051236:CheW protein, Bacteria; D011494:Protein Kinases; D000071677:Histidine Kinase; C000607608:cheA protein, E coli