Not as easy as π: An insertional residue does not explain the π-helix gain-of-function in two-component FMN reductases.

Autor: McFarlane JS; The Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, 66045., Hagen RA; The Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama, 36849., Chilton AS; The Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, 66045., Forbes DL; The Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama, 36849., Lamb AL; The Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, 66045., Ellis HR; The Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama, 36849.
Jazyk: angličtina
Zdroj: Protein science : a publication of the Protein Society [Protein Sci] 2019 Jan; Vol. 28 (1), pp. 123-134. Date of Electronic Publication: 2018 Nov 15.
DOI: 10.1002/pro.3504
Abstrakt: The π-helix located at the tetramer interface of two-component FMN-dependent reductases contributes to the structural divergence from canonical FMN-bound reductases within the NADPH:FMN reductase family. The π-helix in the SsuE FMN-dependent reductase of the alkanesulfonate monooxygenase system has been proposed to be generated by the insertion of a Tyr residue in the conserved α4-helix. Variants of Tyr118 were generated, and their X-ray crystal structures determined, to evaluate how these alterations affect the structural integrity of the π-helix. The structure of the Y118A SsuE π-helix was converted to an α-helix, similar to the FMN-bound members of the NADPH:FMN reductase family. Although the π-helix was altered, the FMN binding region remained unchanged. Conversely, deletion of Tyr118 disrupted the secondary structural properties of the π-helix, generating a random coil region in the middle of helix 4. Both the Y118A and Δ118 SsuE SsuE variants crystallize as a dimer. The MsuE FMN reductase involved in the desulfonation of methanesulfonates is structurally similar to SsuE, but the π-helix contains a His insertional residue. Exchanging the π-helix insertional residue of each enzyme did not result in equivalent kinetic properties. Structure-based sequence analysis further demonstrated the presence of a similar Tyr residue in an FMN-bound reductase in the NADPH:FMN reductase family that is not sufficient to generate a π-helix. Results from the structural and functional studies of the FMN-dependent reductases suggest that the insertional residue alone is not solely responsible for generating the π-helix, and additional structural adaptions occur to provide the altered gain of function.
(© 2018 The Protein Society.)
Databáze: MEDLINE
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