A mechanism-based aryl carrier protein/thiolation domain affinity probe

The design, synthesis, and biochemical characterization of a mechanism-based aryl carrier protein (ArCP) affinity probe that selectively modifies the terminal thiol of the aryl carrier protein phosphopantetheine (Ppant) prosthetic group is described. Labeling of the aryl carrier protein was shown to require the cognate adenylating enzyme to channel the affinity probe onto the Ppant cofactor. The selective labeling was established by observation of the phosphopantetheinyl ejection ion via MS/MS, and the probe was also found to stabilize an interaction between an aryl carrier protein and adenylating enzyme by an electrophoretic mobility shift assay.