Structural Characterization of Complex of Adenylation Domain and Carrier Protein by Using Pantetheine Cross-Linking Probe

Adenylation domains (A-domains) are responsible for selective incorporation of carboxylic acid substrates in the biosynthesis of various natural products. Each A-domain must recognize a cognate carrier protein (CP) for functional substrate transfer. The transient interactions between an A-domain and CP have been investigated by using acyl vinylsulfonamide adenosine inhibitors as probes to determine the structures of several A-domain–CP complexes. However, this strategy requires a specific vinylsulfonamide inhibitor that contains an acyl group corresponding to the substrate specificity of a target A-domain in every case. Here, we report an alternative strategy for structural characterization of A-domain–CP complexes. We used a bromoacetamide pantetheine cross-linking probe in combination with a Cys mutation to trap the standalone A-domain–CP complex involved in macrolactam polyketide biosynthesis through a covalent linkage, allowing the determination of the complex structure. This strategy facilitates the structural determination of A-domain–CP complexes.