Strategy pegs molecules' protein targets

A new strategy may make it easier to identify the protein target of a small-molecule "hit" from a high-throughput phenotypic screen (Chem. Biol. 2006, 13, 443). Target identification remains "a significant problem," notes Jeffrey R. Peterson of Fox Chase Cancer Center in Philadelphia. "What particular protein is the small molecule hitting to get that biological effect?" Peterson and colleagues demonstrate their new method with an inhibitor called pirl1, which they identified in a screen for small molecules that block the assembly of actin fibers in cell extracts. The researchers tested whether they could restore actin fiber assembly in pirl1-treated cell extracts by adding back individual fractions of untreated cell extracts. Repeated rounds of fractionation and testing revealed not only pirl1's target (the protein complex Cdc42/RhoGDI) but also another component of the actin-assembly signaling pathway. Thus, the strategy also should find broad utility as a "tool by which to identify multiple components of a signaling pathway mediating a biological process of interest," they note.