title: Structural and Functional Characterization of a Lytic Polysaccharide Monooxygenase with Broad Substrate Specificity.
abstract: The recently discovered lytic polysaccharide monooxygenases (LPMOs) carry out oxidative cleavage of polysaccharides and are of major importance for efficient processing of biomass. NcLPMO9C from Neurospora crassa acts both on cellulose and on non-cellulose β-glucans, including cellodextrins and xyloglucan. The crystal structure of the catalytic domain of NcLPMO9C revealed an extended, highly polar substrate-binding surface well suited to interact with a variety of sugar substrates. The ability of NcLPMO9C to act on soluble substrates was exploited to study enzyme-substrate interactions. EPR studies demonstrated that the Cu(2+) center environment is altered upon substrate binding, whereas isothermal titration calorimetry studies revealed binding affinities in the low micromolar range for polymeric substrates that are due in part to the presence of a carbohydrate-binding module (CBM1). Importantly, the novel structure of NcLPMO9C enabled a comparative study, revealing that the oxidative regioselectivity of LPMO9s (C1, C4, or both) correlates with distinct structural features of the copper coordination sphere. In strictly C1-oxidizing LPMO9s, access to the solvent-facing axial coordination position is restricted by a conserved tyrosine residue, whereas access to this same position seems unrestricted in C4-oxidizing LPMO9s. LPMO9s known to produce a mixture of C1- and C4-oxidized products show an intermediate situation.
authors.affiliation: From the Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.
authors.forename: Anna S
authors.initials: AS
authors.lastname: Borisova
authors.affiliation: the Department of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences, N-1432 Ås, Norway.
authors.forename: Trine
authors.initials: T
authors.lastname: Isaksen
authors.affiliation: From the Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Dimarogona
authors.affiliation: the Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506.
authors.forename: Abhishek A
authors.initials: AA
authors.lastname: Kognole
authors.affiliation: the Department of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences, N-1432 Ås, Norway.
authors.forename: Geir
authors.initials: G
authors.lastname: Mathiesen
authors.affiliation: the Department of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences, N-1432 Ås, Norway.
authors.forename: Anikó
authors.initials: A
authors.lastname: Várnai
authors.affiliation: the Department of Biosciences, University of Oslo, N-0316 Oslo, Norway, and.
authors.forename: Åsmund K
authors.initials: ÅK
authors.lastname: Røhr
authors.affiliation: From the Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden, the Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Payne
authors.affiliation: the Department of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences, N-1432 Ås, Norway.
authors.forename: Morten
authors.initials: M
authors.lastname: Sørlie
authors.affiliation: From the Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden, mats.sandgren@slu.se.
authors.forename: Mats
authors.initials: M
authors.lastname: Sandgren
authors.affiliation: the Department of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences, N-1432 Ås, Norway, vincent.eijsink@nmbu.no.
authors.forename: Vincent G H
authors.initials: VG
authors.lastname: Eijsink
mesh_terms: D002118:Calcium / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry*; D006899:Mixed Function Oxygenases / Q000737:chemistry*; D009492:Neurospora crassa / Q000201:enzymology*; D011134:Polysaccharides / Q000737:chemistry*; D013379:Substrate Specificity
chemical_list: D005656:Fungal Proteins; D011134:Polysaccharides; D006899:Mixed Function Oxygenases; D002118:Calcium
keywords: biodegradation; bioenergy; copper monooxygenase; crystal structure; electron paramagnetic resonance (EPR); isothermal titration calorimetry (ITC)