Journal:Acta Cryst D:S2059798321006628

Structure of a C1/C4-oxidizing AA9 lytic polysaccharide monooxygenase from the thermophilic fungus Malbranchea cinnamomea

Scott Mazurkewich, Andrea Seveso, Silvia Hüttner, Gisela Brändén, Johan Larsbrink ^[1]

Molecular Tour
The thermophilic fungus Malbranchea cinnamomea encodes eight lytic polysaccharide monooxygenases (LPMOs) from the Auxiliary Activities family 9 (AA9), four of which have been shown to oxidatively cleave various polysaccharides. Here we solved the structure of McAA9F, which is a C1/C4-oxidizing LPMO able to cleave both crystalline and soluble glycans. The structure is colored from N- to C-terminus, blue to red. The copper ion and the residues coordinating it are shown. The loops forming the flat surface comprising the substrate binding face are labelled (L2, L3, L8, LS, LC). The structure reveals that McAA9F has an overall similar fold as other solved AA9 enzymes, but also has different loop structures than what have previously been linked to activity on soluble oligosaccharides.

Comparison of the substrate binding sites of McAA9A and selected AA9 LPMOs, key residues lining the flat surface of:

• McAA9F (PDB entry 7ntl).
• TaAA9A (PDB entry 2yet).
• LsAA9A (PDB entry 5acf).
• CvAA9A in complex with cellohexaose (PDB entry 6yde).

Loop regions corresponding to L2, L3, and LC for each protein are colored green, magenta, and cyan, respectively.

The flat surface of McAA9F.

Superposition of McAA9F, TaAA9A, LsAA9A, and CvAA9A. The key residues lining the flat surface are shown in ball-and-stick representation and are colored: McAA9F in salmon, TaAA9A in lemon chiffon, LsAA9A in yellow, and CvAA9A in hot pink. The other residues are shown as trace and are colored in gainsboro.

The structure further contains a rare succinimide substitution that has not been seen in other LPMOs.

PDB reference: McAA9F, 7ntl.

References

1. ↑ Mazurkewich S, Seveso A, Huttner S, Branden G, Larsbrink J. Structure of a C1/C4-oxidizing AA9 lytic polysaccharide monooxygenase from the thermophilic fungus Malbranchea cinnamomea. Acta Crystallogr D Struct Biol. 2021 Aug 1;77(Pt 8):1019-1026. doi:, 10.1107/S2059798321006628. Epub 2021 Jul 29. PMID:34342275 doi:http://dx.doi.org/10.1107/S2059798321006628