Structure, 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: 10.1016/j.jmb.2017.10.015
- Primary Citation of Related Structures:
- 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 d ...
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 KD=62±13nM, followed by the binding of two more equivalents of holo-ACPP with KD=1.2±0.2μM. Cooperativity was not observed for apo-ACPP which bound with KD=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.
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.