5KP8

Crystal Structure of the Curacin Biosynthetic Pathway HMG Synthase in Complex with Acetyl Donor-ACP

Summary for 5KP8

• Entry DOI: 10.2210/pdb5kp8/pdb
• Related: 5KP5 5KP6 5KP7
• Descriptor: CurD, CurB, 4'-PHOSPHOPANTETHEINE, ... (5 entities in total)
• Functional Keywords: hmg synthase, enzyme-acp complex, transferase
• Biological source: Moorea producens 3L; More
• Total number of polymer chains: 2
• Total formula weight: 61436.48

Authors

Maloney, F.P.,Smith, J.L. (deposition date: 2016-07-02, release date: 2016-08-31, Last modification date: 2023-10-04)

Primary citation

Maloney, F.P.,Gerwick, L.,Gerwick, W.H.,Sherman, D.H.,Smith, J.L.
Anatomy of the beta-branching enzyme of polyketide biosynthesis and its interaction with an acyl-ACP substrate.
Proc.Natl.Acad.Sci.USA, 113:10316-10321, 2016

PubMed Abstract: Alkyl branching at the β position of a polyketide intermediate is an important variation on canonical polyketide natural product biosynthesis. The branching enzyme, 3-hydroxy-3-methylglutaryl synthase (HMGS), catalyzes the aldol addition of an acyl donor to a β-keto-polyketide intermediate acceptor. HMGS is highly selective for two specialized acyl carrier proteins (ACPs) that deliver the donor and acceptor substrates. The HMGS from the curacin A biosynthetic pathway (CurD) was examined to establish the basis for ACP selectivity. The donor ACP (CurB) had high affinity for the enzyme (Kd = 0.5 μM) and could not be substituted by the acceptor ACP. High-resolution crystal structures of HMGS alone and in complex with its donor ACP reveal a tight interaction that depends on exquisite surface shape and charge complementarity between the proteins. Selectivity is explained by HMGS binding to an unusual surface cleft on the donor ACP, in a manner that would exclude the acceptor ACP. Within the active site, HMGS discriminates between pre- and postreaction states of the donor ACP. The free phosphopantetheine (Ppant) cofactor of ACP occupies a conserved pocket that excludes the acetyl-Ppant substrate. In comparison with HMG-CoA (CoA) synthase, the homologous enzyme from primary metabolism, HMGS has several differences at the active site entrance, including a flexible-loop insertion, which may account for the specificity of one enzyme for substrates delivered by ACP and the other by CoA.

PubMed: 27573844
DOI: 10.1073/pnas.1607210113

Experimental method

X-RAY DIFFRACTION (1.9 Å)