PURIFICATION AND ANALYSIS OF PROFILIN LIGANDS FROM COMPLEX CELLULAR LYSATES

Abstract

Profilin is a ubiquitous actin-binding protein that regulates actin-polymerization, and forms the hub of various protein-interaction networks. It binds polyproline-rich motifs on its ligands. This interaction harnesses the profilin-actin complex for assembly into actin filaments’ various processes. In this work, profilin ligands are enriched and identified from complex cellular lysates such as cell cultures and organ extracts, using quantitative mass spectrometry (MS). Profilin is evaluated for its ability to interact with its ligands in the presence and absence of actin, using SILAC and fluorescence anisotropy. Profilin ligands from organ extracts were identified by the dimethyl labeling (DML) approach. Based on tandem affinity purification (TAP-TAG) strategy, the project was further extended as a purification approach targeting profilin ligands. Results from SILAC showed that profilin consistently enriched actin, actin-filament elongating proteins, and actin-nucleating ligands. MS data from an actin-binding-site mutant of profilin suggested that profilin doesn’t require actin to bind its ligands.