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

Abstract

When covalently linked to an acyl carrier protein (ACP) and loaded with acyl substrate-mimics, some 4′-phosphopantetheine prosthetic group arms swing freely, whereas others stick to the protein surface, suggesting a possible mode of interaction with enzyme domains during polyketide biosynthesis.

Structural and dynamic characterization of a freestanding acyl carrier protein involved in the biosynthesis of cyclic lipopeptide antibiotics

“…Unfolding studies of the apo‐ and holo‐forms of Plasmodium falciparum ACP revealed that the holo‐form had greater stability than its apo‐counterpart due to hydrophobic interactions between the protein and the prosthetic group . However, an increase in the melting temperature was also observed for an holo‐ACP form of the mycolactone polyketide synthase from Mycobacterium ulcerans where the phosphopantetheine moiety appeared to swing freely around the highly conserved attachment site . In our study, we also investigated the effect of attached phosphopantetheine on protein stability.…”

“…40 However, an increase in the melting temperature was also observed for an holo-ACP form of the mycolactone polyketide synthase from Mycobacterium ulcerans where the phosphopantetheine moiety appeared to swing freely around the highly conserved attachment site. 41 In our study, we also investigated the effect of attached phosphopantetheine on protein stability. The DSC data (Table I) indicate a substantial increase in the melting temperature for holo-LipD in the EDTA-chelated form.…”

Substrate-bound structures of a ketoreductase from amphotericin modular polyketide synthase

“…Complex polyketides harbor numerous methyl groups possessing L stereochemistry, whereas the KSs of modular PKSs catalyze the generation of (2D)-2-methyl-3-ketoacyl-ACPs exclusively during the elongation of polyketide intermediates (Castonguay et al, 2007; Weissman et al, 1997; Xie et al, 2017). In addition, the binding of the acyl group to a patch on the surface of the ACP prevents the water-catalyzed epimerization observed for the C2 methyl group of the NAC- or pantetheine-bound thioesters (Castonguay et al, 2007; Vance et al, 2016). The EIX assays provide direct evidence that A2- and B2-type KRs have intrinsic epimerase activities.…”

Dissecting how modular polyketide synthase ketoreductases interact with acyl carrier protein-attached substrates

“…The experiments described above demonstrate that the interaction between an acyl-ACP species and a KR/cofactor binary complex is multivalent, comprising distinct contributions from the ACP surface, the prosthetic group and the thioester-linked substrate. However, the increase in affinity observed when the Ppant and acyl moieties are included is relatively small, indicating that the entropic penalties engendered by restricting the motion of the freely swinging prosthetic group arm 25 are only just compensated for by the favourable enthalpy change resulting from extension of the binding interface. The net effect is likely to be an increase in the specificity of the interaction (due to contacts with multiple binding sites), but with only minor effects on the dissociation constant.…”