Download MendeleyStructure, High Affinity, and Negative Cooperativity of the Escherichia coli Holo-(Acyl Carrier Protein):Holo-(Acyl Carrier Protein) Synthase Complex.
Marcella, A.M., Culbertson, S.J., Shogren-Knaak, M.A., Barb, A.W.(2017) J Mol Biol 429: 3763-3775
- PubMed: 29054754
- DOI: https://doi.org/10.1016/j.jmb.2017.10.015
- Primary Citation of Related Structures:
5VBX, 5VCB - PubMed Abstract:
The Escherichia coli holo-(acyl carrier protein) synthase (ACPS) catalyzes the coenzyme A-dependent activation of apo-ACPP to generate holo-(acyl carrier protein) (holo-ACPP) in an early step of fatty acid biosynthesis. E. coli ACPS is sufficiently different from the human fatty acid synthase to justify the development of novel ACPS-targeting antibiotics. Models of E. coli ACPS in unliganded and holo-ACPP-bound forms solved by X-ray crystallography to 2.05and 4.10Å, respectively, revealed that ACPS bound three product holo-ACPP molecules to form a 3:3 hexamer. Solution NMR spectroscopy experiments validated the ACPS binding interface on holo-ACPP using chemical shift perturbations and by determining the relative orientation of holo-ACPP to ACPS by fitting residual dipolar couplings. The binding interface is organized to arrange contacts between positively charged ACPS residues and the holo-ACPP phosphopantetheine moiety, indicating product contains more stabilizing interactions than expected in the enzyme:substrate complex. Indeed, holo-ACPP bound the enzyme with greater affinity than the substrate, apo-ACPP, and with negative cooperativity. The first equivalent of holo-ACPP bound with a K D =62±13nM, followed by the binding of two more equivalents of holo-ACPP with K D =1.2±0.2μM. Cooperativity was not observed for apo-ACPP which bound with K D =2.4±0.1μM. Strong product binding and high levels of holo-ACPP in the cell identify a potential regulatory role of ACPS in fatty acid biosynthesis.
Organizational Affiliation:
Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, 2437 Pammel Drive, Molecular Biology Building, rm 4210, Iowa State University, Ames, IA 50011, United States.
