(A) Using denaturing immunoprecipitation (IP), Munc18-1 was isolated from cell lysate of HEK293T cells expressing M18WT, M18Y145F or M18Y473F together with or without n-Src. Munc18-1 was immunoblotted for tyrosine phosphorylation using the 4G10 antibody (αPtyr), after which the blot was stripped and re-blotted for Munc18-1. Total lysate (TL) is shown as loading control. N-Src was tagged with a flag-tag for visualization. 