ABRF-PRG04: differentiation of protein isoforms

Area of Science:

• Proteomics
• Biochemistry
• Analytical Chemistry

Background:

• Accurate protein identification is crucial, especially for distinguishing closely related protein isoforms.
• Isoforms can differ by single amino acid substitutions or post-translational modifications, posing identification challenges.

Purpose of the Study:

• To assess laboratory capabilities in protein identification using a mixture of three closely related proteins.
• To evaluate different sample fractionation, protein digestion, and protein identification strategies.
• To determine the accuracy of identifying protein isoforms and post-translational modifications.

Main Methods:

• A mixture of three picomoles each of three closely related proteins was distributed to participating laboratories.
• Laboratories employed various techniques including 1D- or 2D-PAGE, HPLC for fractionation, in-solution or in-gel digestion, and mass spectrometry for identification.
• Data analysis involved instrumentation, software, and manual interpretation for protein identification and modification determination.

Main Results:

• Only 19% of 42 participating laboratories correctly identified all three protein isoforms and their N-terminal acetylation.
• 38% correctly identified two isoforms, while 21% identified two but also made incorrect identifications.
• 21% of labs failed to make any correct protein identifications, indicating variability in performance.

Conclusions:

• Significant challenges exist in accurately identifying and distinguishing closely related protein isoforms.
• The study revealed variability in laboratory practices and the effectiveness of different proteomics workflows.
• Improvements in mass spectrometry-based proteomics strategies are needed for reliable isoform and post-translational modification analysis.