7K14

Ternary soak structure of alkanesulfonate monooxygenase MsuD from Pseudomonas fluorescens with FMN and methanesulfonate

Summary for 7K14

• Entry DOI: 10.2210/pdb7k14/pdb
• Related: 7JV3 7JW9 7JYB 7K64
• Descriptor: Alkanesulfonate monooxygenase, FLAVIN MONONUCLEOTIDE, methanesulfonic acid, ... (6 entities in total)
• Functional Keywords: tim barrel, flavin monooxygenase, flavoprotein, oxidoreductase
• Biological source: Pseudomonas fluorescens
• Total number of polymer chains: 8
• Total formula weight: 358071.91

Authors

Liew, J.J.M.,Dowling, D.P.,El Saudi, I.M. (deposition date: 2020-09-07, release date: 2021-05-26, Last modification date: 2023-10-18)

Primary citation

Liew, J.J.M.,El Saudi, I.M.,Nguyen, S.V.,Wicht, D.K.,Dowling, D.P.
Structures of the alkanesulfonate monooxygenase MsuD provide insight into C-S bond cleavage, substrate scope, and an unexpected role for the tetramer.
J.Biol.Chem., 297:100823-100823, 2021

PubMed Abstract: Bacterial two-component flavin-dependent monooxygenases cleave the stable C-S bond of environmental and anthropogenic organosulfur compounds. The monooxygenase MsuD converts methanesulfonate (MS) to sulfite, completing the sulfur assimilation process during sulfate starvation, but the mechanism of this conversion remains unclear. To explore the mechanism of C-S bond cleavage, we report a series of crystal structures of MsuD from Pseudomonas fluorescens in different liganded states. This report provides the first crystal structures of an alkanesulfonate monooxygenase with a bound flavin and alkanesulfonate, elucidating the roles of the active site lid, the protein C terminus, and an active site loop in flavin and/or alkanesulfonate binding. These structures position MS closest to the flavin N5 position, consistent with an N5-(hydro)peroxyflavin mechanism rather than a classical C4a-(hydro)peroxyflavin mechanism. A fully enclosed active site is observed in the ternary complex, mediated by interchain interaction of the C terminus at the tetramer interface. These structures identify an unexpected function of the protein C terminus in this protein family in stabilizing tetramer formation and the alkanesulfonate-binding site. Spurred by interest from the crystal structures, we conducted biochemical assays and molecular docking that redefine MsuD as a small- to medium-chain alkanesulfonate monooxygenase. Functional mutations verify the sulfonate-binding site and reveal the critical importance of the protein C terminus for monooxygenase function. These findings reveal a deeper understanding of MsuD's functionality at the molecular level and consequently how it operates within its role as part of the sulfur assimilation pathway.

PubMed: 34029591
DOI: 10.1016/j.jbc.2021.100823

Experimental method

X-RAY DIFFRACTION (2.75 Å)