Conformational flexibility of EptA driven by an interdomain helix provides insights for enzyme–substrate recognition

• Published in: IUCrJ Vol. 8; no. 5; pp. 732 - 746
• Main Authors: Anandan, Anandhi, Dunstan, Nicholas W, Ryan, Timothy M, Mertens, Haydyn D.T, Lim, Katherine Y.L, Evans, Genevieve L, Kahler, Charlene M, Vrielink, Alice
• Format: Journal Article
• Language: English
• Published: Chester International Union of Crystallography 01-09-2021
• Subjects: Antiinfectives and antibacterials; conformational flexibility; Detergents, Synthetic; Domains; Drug resistance in microorganisms; Endotoxins; enzyme substrate recognition; Enzymes; epta; Flexibility; Fluorescence; Lipids; Micelles; Peptides; phosphoethanolamine transferase; Quenching; Research Papers; Scattering; small-angle x-ray scattering; Substrates; Tryptophan; tryptophan fluorescence; Australia
• ISSN: 2052-2525; 2052-2525
• DOI: 10.1107/S2052252521005613

Many pathogenic gram-negative bacteria have developed mechanisms to increase resistance to cationic antimicrobial peptides by modifying the lipid A moiety. One modification is the addition of phosphoethanolamine to lipid A by the enzyme phosphoethanolamine transferase (EptA). Previously we reported the structure of EptA from
Neisseria
, revealing a two-domain architecture consisting of a periplasmic facing soluble domain and a transmembrane domain, linked together by a bridging helix. Here, the conformational flexibility of EptA in different detergent environments is probed by solution scattering and intrinsic fluorescence-quenching studies. The solution scattering studies reveal the enzyme in a more compact state with the two domains positioned close together in an
n
-dodecyl-β-D-maltoside micelle environment and an open extended structure in an
n
-dodecyl-phosphocholine micelle environment. Intrinsic fluorescence quenching studies localize the domain movements to the bridging helix. These results provide important insights into substrate binding and the molecular mechanism of endotoxin modification by EptA.