HPLC method to resolve, identify and quantify guanine nucleotides bound to recombinant ras GTPase

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Signaling

Background:

• Ras small G proteins are crucial regulators of cellular signaling pathways.
• Their activity is controlled by GTP/GDP binding, acting as molecular switches.
• Accurate assessment of nucleotide-bound states is vital for in vitro functional studies.

Purpose of the Study:

• To develop and validate a robust method for analyzing the bound nucleotide composition of Ras G proteins.
• To quantify fractional activation states (GTP-bound vs. GDP-bound) in vitro.
• To investigate the molecular mechanisms underlying Ras mutations.

Main Methods:

• Nucleotide loading of Ras proteins with GTP analogs (GMPPNP) or GDP.
• Washing to remove unbound nucleotides.
• Heat extraction of bound nucleotides.
• Ion-paired, reverse-phase HPLC-UV for nucleotide resolution, identification, and quantification.

Main Results:

• A highly reproducible method for analyzing bound nucleotide composition was established.
• The method accurately quantifies GTP and GDP bound to Ras proteins.
• Fractional on- and off-state populations were resolved, confirming method efficacy.
• Novel hypotheses for Ras mutation disease mechanisms at E63 and Y64 were generated.

Conclusions:

• The developed method provides precise quantification of Ras G protein nucleotide states.
• This technique is essential for accurate in vitro functional analysis of Ras proteins.
• The findings offer new insights into the molecular basis of Ras-related diseases.