Absolute Quantitation of GTPase Protein Abundance

Area of Science:

• Molecular Biology
• Proteomics
• Cellular Signaling

Background:

• Ras proteins and other small GTPases act as crucial molecular switches in cellular functions.
• High homology and functional redundancy among related GTPases complicate expression analysis.
• Current antibody-based methods are often semi-quantitative and unsuitable for comparing different gene products.

Purpose of the Study:

• To develop a precise, quantitative method for determining protein copy number per cell.
• To enable accurate comparative analysis of protein expression across different genes.
• To provide a robust protocol for absolute protein quantitation.

Main Methods:

• Development of a mass spectrometry-based quantification strategy.
• Generation of isotopically labeled protein standards for accurate measurement.
• Detailed protocols for sample processing and mass spectrometry optimization.
• Application to quantify specific small GTPases (HRAS, KRAS4A, KRAS4B, NRAS, RALA, RALB).

Main Results:

• The presented method allows for precise quantification of protein copy number per cell.
• Demonstrated successful application in cell line and tissue-derived samples.
• Provides a reliable alternative to semi-quantitative antibody-based approaches.

Conclusions:

• Mass spectrometry offers a powerful tool for absolute protein quantitation.
• The developed method facilitates accurate comparative analysis of small GTPase expression.
• This technique is valuable for studying cellular functions regulated by small molecular weight GTPases.