Structural and functional characterization of the catalytic domain of a cell-wall anchored bacterial lytic polysaccharide monooxygenase from Streptomyces coelicolor

• Published in: Scientific reports 2023-04, Vol.13 (1), p.5345-5345, Article 5345
• Main Authors: Votvik, Amanda K., Røhr, Åsmund K., Bissaro, Bastien, Stepnov, Anton A., Sørlie, Morten, Eijsink, Vincent G. H., Forsberg, Zarah
• Format: Article
• Language: English
• Subjects: 631/45; 631/45/535; 631/45/607; 631/535/1266; Bacteria; C-Terminus; Catalytic Domain; Cell Wall - metabolism; Cell walls; Cellulose; Chitin; Chitin - chemistry; Crystal structure; Enzymes; Genomes; Humanities and Social Sciences; Life Sciences; Mixed Function Oxygenases - metabolism; multidisciplinary; Phylogeny; Polymers; Polysaccharides; Polysaccharides, Bacterial; Science; Science (multidisciplinary); Streptomyces coelicolor; Streptomyces coelicolor - metabolism; Structure-function relationships
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-023-32263-7

Bacterial lytic polysaccharide monooxygenases (LPMOs) are known to oxidize the most abundant and recalcitrant polymers in Nature, namely cellulose and chitin. The genome of the model actinomycete Streptomyces coelicolor A3(2) encodes seven putative LPMOs, of which, upon phylogenetic analysis, four group with typical chitin-oxidizing LPMOs, two with typical cellulose-active LPMOs, and one which stands out by being part of a subclade of non-characterized enzymes. The latter enzyme, called Sc LPMO10D, and most of the enzymes found in this subclade are unique, not only because of variation in the catalytic domain, but also as their C-terminus contains a cell wall sorting signal (CWSS), which flags the LPMO for covalent anchoring to the cell wall. Here, we have produced a truncated version of Sc LPMO10D without the CWSS and determined its crystal structure, EPR spectrum, and various functional properties. While showing several structural and functional features typical for bacterial cellulose active LPMOs, Sc LPMO10D is only active on chitin. Comparison with two known chitin-oxidizing LPMOs of different taxa revealed interesting functional differences related to copper reactivity. This study contributes to our understanding of the biological roles of LPMOs and provides a foundation for structural and functional comparison of phylogenetically distant LPMOs with similar substrate specificities.