Effect of carrier protein identity on CP-FabA crosslinking. 3-decynoyl pantetheine 1 was used to modify the carrier proteins AcpP (FAS), Fren (PKS), Otc (PKS), and EntB (NRPS). Upon addition of FabA, crosslinking is observed only with AcpP, Fren, and Otc, indicating the preferential interaction of FabA with 3-decynoyl-acyl carrier proteins over peptidyl carrier proteins.