Rapid phosphotransfer to CheY from a CheA protein lacking the CheY-binding domain

Area of Science:

• Biochemistry
• Molecular Biology
• Microbiology

Background:

• Bacterial chemotaxis relies on signal transduction pathways.
• Histidine protein kinase CheA is crucial for transmitting chemotaxis signals.
• CheA autophosphorylates and transfers phosphate to CheY, influencing flagellar rotation.

Purpose of the Study:

• To investigate the role of the P2 domain of CheA in the phosphotransfer reaction with CheY.
• To quantify the kinetic contribution of the CheA P2 domain to CheY phosphorylation.

Main Methods:

• Utilized rapid-quench and stopped-flow fluorescence experiments.
• Compared phosphotransfer kinetics between wild-type CheA and a mutant lacking the P2 domain (CheADeltaP2).

Main Results:

• The CheADeltaP2 mutant exhibited significantly slower reaction rates and a higher K(m) compared to wild-type CheA.
• The catalytic efficiency (k(cat)/K(m)) of CheADeltaP2 was substantially lower than that of wild-type CheA.
• Despite the reduction, CheADeltaP2 phosphotransfer remained much faster than reactions with small molecule phosphodonors.

Conclusions:

• The P2 domain of CheA plays a vital role in facilitating rapid phosphotransfer to CheY by binding CheY.
• The P1 domain of CheA also contributes significantly to the overall phosphotransfer rates in chemotaxis.
• These findings elucidate the molecular mechanisms underlying bacterial chemotaxis signal transduction.