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Sticky swinging arm dynamics: studies of an acyl carrier protein domain from the mycolactone polyketide synthase.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Vance, Steven 
Tkachenko, Olga 
Thomas, Ben 
Bassuni, Mona 
Hong, Hui 

Abstract

Type I modular polyketide synthases (PKSs) produce polyketide natural products by passing a growing acyl substrate chain between a series of enzyme domains housed within a gigantic multifunctional polypeptide assembly. Throughout each round of chain extension and modification reactions, the substrate stays covalently linked to an acyl carrier protein (ACP) domain. In the present study we report on the solution structure and dynamics of an ACP domain excised from MLSA2, module 9 of the PKS system that constructs the macrolactone ring of the toxin mycolactone, cause of the tropical disease Buruli ulcer. After modification of apo ACP with 4'-phosphopantetheine (Ppant) to create the holo form, (15)N nuclear spin relaxation and paramagnetic relaxation enhancement (PRE) experiments suggest that the prosthetic group swings freely. The minimal chemical shift perturbations displayed by Ppant-attached C3 and C4 acyl chains imply that these substrate-mimics remain exposed to solvent at the end of a flexible Ppant arm. By contrast, hexanoyl and octanoyl chains yield much larger chemical shift perturbations, indicating that they interact with the surface of the domain. The solution structure of octanoyl-ACP shows the Ppant arm bending to allow the acyl chain to nestle into a nonpolar pocket, whereas the prosthetic group itself remains largely solvent exposed. Although the highly reduced octanoyl group is not a natural substrate for the ACP from MLSA2, similar presentation modes would permit partner enzyme domains to recognize an acyl group while it is bound to the surface of its carrier protein, allowing simultaneous interactions with both the substrate and the ACP.

Description

Keywords

4′-phosphopantetheine, NMR spectroscopy, acyl carrier protein, mycolactone, type I polyketide synthase, Acyl Carrier Protein, Macrolides, Mycobacterium ulcerans, Polyketide Synthases, Protein Structure, Secondary, Protein Structure, Tertiary

Journal Title

Biochemical Journal

Conference Name

Journal ISSN

0264-6021
1470-8728

Volume Title

473

Publisher

Portland Press, Ltd.
Sponsorship
Wellcome Trust (094252/Z/10/Z)
Biotechnology and Biological Sciences Research Council (BB/E013228/1)
This work was supported by the Wellcome Trust [grant number 094252/Z/10/Z]. The Yousef Jameel Academic Foundation and the Cambridge Trust are thanked for providing a studentship to M.B.