Michaelis-Menten kinetics of RasGAP proteins by a rapid fluorescence-based assay

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Signaling

Background:

• Ras small GTPases are crucial regulators of cellular processes.
• GTPase activating proteins (GAPs) are essential for GTP hydrolysis in Ras proteins.
• Accurate kinetic profiling of Ras-GAP interactions is vital for understanding cellular regulation.

Purpose of the Study:

• To develop and present a protocol for Michaelis-Menten kinetic profiling of small GTPase activation by GAPs.
• To enable real-time monitoring of inorganic phosphate release using fluorescence-based detection.
• To provide a comprehensive method for studying Ras-GAP interactions in vitro.

Main Methods:

• Utilized a fluorescence-based assay employing the Phosphate Sensor protein (MDCC conjugate with PstS).
• Monitored inorganic phosphate release in real-time to quantify GTPase activity.
• Applied the protocol to H-Ras GTPase stimulated by p120RasGAP (RasGAP, RASA1).

Main Results:

• Established a convenient and comprehensive protocol for kinetic profiling of Ras-GAP activity.
• Demonstrated the ability to perform up to twenty simultaneous reactions with phosphate production rates in the nM/s range.
• Provided guidelines for optimizing reagent conditions, including salt concentrations, and assessing their impact.

Conclusions:

• The developed protocol offers an accurate and accessible method for monitoring small GTPase activation by GAPs.
• This technique utilizes widely available materials and is adaptable to various research applications.
• Facilitates a deeper understanding of the kinetics governing Ras-GAP protein interactions.