Conserved cysteine residues provide a protein-protein interaction surface in dual oxidase (DUOX) proteins.
Intramolecular disulfide bond formation is promoted in oxidizing extracellular and endoplasmic reticulum compartments and often contributes to protein stability and function. DUOX1 and DUOX2 are distinguished from other members of the NOX protein family by the presence of a unique extracellular N-terminal region. These peroxidase-like domains lack the conserved cysteines that confer structural stability to mammalian peroxidases. Sequence-based structure predictions suggest that the thiol groups present are solvent-exposed on a single protein surface and are too distant to support intramolecular disulfide bond formation. To investigate the role of these thiol residues, we introduced four individual cysteine to glycine mutations in the peroxidase-like domains of both human DUOXs and purified the recombinant proteins. The mutations caused little change in the stabilities of the monomeric proteins, supporting the hypothesis that the thiol residues are solvent-exposed and not involved in disulfide bonds that are critical for structural integrity. However, the ability of the isolated hDUOX1 peroxidase-like domain to dimerize was altered, suggesting a role for these cysteines in protein-protein interactions that could facilitate homodimerization of the peroxidase-like domain or, in the full-length protein, heterodimeric interactions with a maturation protein. When full-length hDUOX1 was expressed in HEK293 cells, the mutations resulted in decreased H2O2 production that correlated with a decreased amount of the enzyme localized to the membrane surface rather than with a loss of activity or with a failure to synthesize the mutant proteins. These results support a role for the cysteine residues in intermolecular disulfide bond formation with the DUOX maturation factor DUOXA1.
Laboratory of Molecular Pharmacology of the Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.
Jennifer L
JL
Meitzler
Sara
S
Hinde
Botond
B
Bánfi
William M
WM
Nauseef
Paul R
PR
Ortiz de Montellano
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000074623:Dual Oxidases; D004591:Electrophoresis, Polyacrylamide Gel; D057809:HEK293 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D019255:NADPH Oxidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D061987:Sf9 Cells; D013050:Spectrometry, Fluorescence; D013499:Surface Properties
D008565:Membrane Proteins; D011994:Recombinant Proteins; D006861:Hydrogen Peroxide; D000074623:Dual Oxidases; D019255:NADPH Oxidases; C431513:DUOX1 protein, human; C431515:DUOX2 protein, human; D003545:Cysteine