Evaluating Calmodulin-Protein Interactions by Rapid Photoactivated Cross-Linking in Live Cells Metabolically Labeled with Photo-Methionine.

This work addresses the question of how the Ca sensor protein calmodulin shapes cellular responses to Ca signals. Proteins interacting with affinity tagged calmodulin were captured by rapid ( ≈ 7 s) photoactivated cross-linking under basal conditions, after brief removal of extracellular Ca and during a cytosolic [Ca] transient in cells metabolically labeled with a photoreactive methionine analog. Tagged adducts were stringently enriched, and captured proteins were identified and quantified by LC-MS/MS.