Abstract

SidA (siderophore A) is a flavin-dependent N-hydroxylating monooxygenase that is essential for virulence in Aspergillus fumigatus. SidA catalyzes the NADPH- and oxygen-dependent formation of N5-hydroxyornithine. In this reaction, NADPH reduces the flavin, and the resulting NADP+ is the last product to be released. The presence of NADP+ is essential for activity, as it is required for stabilization of the C4a-hydroperoxyflavin, which is the hydroxylating species. As part of our efforts to determine the molecular details of the role of NADP(H) in catalysis, we targeted Ser-257 for site-directed mutagenesis and performed extensive characterization of the S257A enzyme. Using a combination of steady-state and stopped-flow kinetic experiments, substrate analogs, and primary kinetic isotope effects, we show that the interaction between Ser-257 and NADP(H) is essential for stabilization of the C4a-hydroperoxyflavin. Molecular dynamics simulation results suggest that Ser-257 functions as a pivot point, allowing the nicotinamide of NADP + to slide into position for stabilization of the C4a-hydroperoxyflavin. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.

Department(s)

Chemistry

Publication Status

Open Access

Comments

National Science Foundation, Grant MCB 1021384

International Standard Serial Number (ISSN)

1083-351X; 0021-9258

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2024 Elsevier; American Society for Biochemistry and Molecular Biology, All rights reserved.

Creative Commons Licensing

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Publication Date

08 Nov 2013

PubMed ID

24072704

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