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Specificity residues determine binding affinity for two-component signal transduction systems. mBio 2013 Nov 05;4(6):e00420-13

Date

11/07/2013

Pubmed ID

24194534

Pubmed Central ID

PMC3892784

DOI

10.1128/mBio.00420-13

Scopus ID

2-s2.0-84891612853   27 Citations

Abstract

UNLABELLED: Two-component systems (TCS) comprise histidine kinases and their cognate response regulators and allow bacteria to sense and respond to a wide variety of signals. Histidine kinases (HKs) phosphorylate and dephosphorylate their cognate response regulators (RRs) in response to stimuli. In general, these reactions appear to be highly specific and require an appropriate association between the HK and RR proteins. The Myxococcus xanthus genome encodes one of the largest repertoires of signaling proteins in bacteria (685 open reading frames [ORFs]), including at least 127 HKs and at least 143 RRs. Of these, 27 are bona fide NtrC-family response regulators, 21 of which are encoded adjacent to their predicted cognate kinases. Using system-wide profiling methods, we determined that the HK-NtrC RR pairs display a kinetic preference during both phosphotransfer and phosphatase functions, thereby defining cognate signaling systems in M. xanthus. Isothermal titration calorimetry measurements indicated that cognate HK-RR pairs interact with dissociation constants (Kd) of approximately 1 µM, while noncognate pairs had no measurable binding. Lastly, a chimera generated between the histidine kinase, CrdS, and HK1190 revealed that residues conferring phosphotransfer and phosphatase specificity dictate binding affinity, thereby establishing discrete protein-protein interactions which prevent cross talk. The data indicate that binding affinity is a critical parameter governing system-wide signaling fidelity for bacterial signal transduction proteins.

IMPORTANCE: Using in vitro phosphotransfer and phosphatase profiling assays and isothermal titration calorimetry, we have taken a system-wide approach to demonstrate specificity for a family of two-component signaling proteins in Myxococcus xanthus. Our results demonstrate that previously identified specificity residues dictate binding affinity and that phosphatase specificity follows phosphotransfer specificity for cognate HK-RR pairs. The data indicate that preferential binding affinity is the basis for signaling fidelity in bacterial two-component systems.

Author List

Willett JW, Tiwari N, Müller S, Hummels KR, Houtman JC, Fuentes EJ, Kirby JR

Author

John Kirby PhD Chair, Center Associate Director, Professor in the Microbiology and Immunology department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Gene Order
Histidine Kinase
Kinetics
Myxococcus xanthus
Protein Binding
Protein Kinases
Signal Transduction
Substrate Specificity
Transcription Factors