Journal:Acta Cryst D:S2059798322004612
From Proteopedia
Structural Visualization of Transient Interactions Between the cis-acting Acyltransferase and Acyl Carrier Protein of Salinomycin Modular Polyketide SynthaseY. Feng, F. Zhang, S. Huang, Z. Deng, L. Bai and J. Zheng [1] Molecular Tour The apparent architectural modularity encourages the construction of hybrid mPKSs to generate unnatural polyketides. The cis-AT domains control the acyl unit incorporated into every elongation step and therefore are attractive engineering targets. This highlights the need for more careful consideration of proper AT-ACP interactions in engineering mPKSs. The inherently transient and weak nature is the key challenge in understanding protein-protein interactions between AT and ACP. The weak mutual binding affinity hampers the structural determination of a AT-ACP complex for directly visualization of protein-protein interactions. We reported the crystal structure of a (PDB ID: 7vrs) from the 9th extension module of a salinomycin mPKS. SalAT9 is organized into a large α,β-hydrolase subdomain (residues 97−224 and 299−418) and a small ferredoxin-like subdomain (residues 228−294). The N-terminal KS-to-AT linker (residues 1-92) forms a three-stranded antiparallel β-sheet and three α-helices, packing against the AT domain. The transient cis-AT-ACP complex was obtained by using 1,4-bis(maleimido)butane (BMB) as a crosslinking agent. . The ACP-binding mode in the cis-AT-ACP complex structure is strikingly different from those of the previously reported trans-AT-ACP complex structures. The ACP primarily contacts the large subdomain of the AT in structure of the cis-AT-ACP complex, whereas the ACP primarily contacts the small domain of the AT in the trans-AT-ACP complex structures. The complex structure provides detailed mechanistic insights into the protein-protein interactions between AT and ACP domains of cis-AT mPKSs and could potentially help optimize chimeric cis-AT mPKSs for unnatural polyketides. SalAT9M large hydrolase subdomain (in dark turquoise) functions as the major binding platform for SalACP9 (in burlywood): . with an angle of 26°. . In the crystallographic asymmetric unit, a and a molecule were observed. .
The KS-to-AT linkers have been shown to functional as a structural element stabilizing the ATs that is expressed as standalone domains. The absence or incompleteness of KS-to-AT linkers in AT constructs may result in insoluble or inactive proteins. The complex structure shows that . PDB references: The complex of Acyltransferase and Acyl Carrier Protein Domains from module 9 of Salinomycin Polyketide Synthase, 7vrs; Acyltransferase from the 9th Module of Salinomycin Polyketide Synthase, 7vt1. References
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