Isolation of signal transduction complexes using biotin and crosslinking methodologies.

We have developed a strategy to preferentially label the N-terminal alpha-amino groups of intact proteins allowing the internal epsilon-amino groups to remain free to react with chemical crosslinking reagents. The convergence of these methodologies allows biotinylated ligands to bind to their receptors within the cell membrane followed by removal of the crosslinked complex from cell lysate. This technique allows for the isolation of protein complexes in an MS-compatible system, thus providing a tool for furthering our understanding of signal transduction.