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Publication Abstract from PubMed

The recently discovered lytic polysaccharide monooxygenases (LPMOs) are Cu-containing enzymes capable of degrading polysaccharide substrates oxidatively. The generally accepted first step in the LPMO reaction is the reduction of the active-site metal ion from Cu(2+) to Cu(+). Here we have used a systematic diffraction data collection method to monitor structural changes in two AA9 LPMOs, one from Lentinus similis (LsAA9_A) and one from Thermoascus auranti-acus (TaAA9_A), as the active-site Cu is photoreduced in the X-ray beam. For LsAA9_A, the protein produced in two different recombinant systems was crystallized to probe the effect of post-translational modifications and different crystallization conditions on the active site and metal photoreduction. We can recommend that crystallographic studies of AA9 LPMOs wishing to address the Cu(2+) form use a total X-ray dose below 3 x 10(4) Gy, while the Cu(+) form can be attained using 1 x 10(6) Gy. In all cases, we observe the transition from a hexa-coordinated Cu site with two solvent-facing ligands to a T-shaped geometry with no exogenous ligands, and a clear increase of the theta2 parameter and a decrease of the theta3 parameter by averages of 9.2 degrees and 8.4 degrees , respectively, but also a slight increase in thetaT. Thus, the theta2 and theta3 parameters are helpful diagnostics for the oxidation state of the metal in a His-brace protein. On binding of cello-oligosaccharides to LsAA9_A, regardless of the production source, the thetaT parameter increases, making the Cu site less planar, while the active-site Tyr-Cu distance decreases reproducibly for the Cu(2+) form. Thus, the thetaT increase found on copper reduction may bring LsAA9_A closer to an oligosaccharide-bound state and contribute to the observed higher affinity of reduced LsAA9_A for cellulosic substrates.

Changes in active-site geometry on X-ray photoreduction of a lytic polysaccharide monooxygenase active-site copper and saccharide binding.,Tandrup T, Muderspach SJ, Banerjee S, Santoni G, Ipsen JO, Hernandez-Rollan C, Norholm MHH, Johansen KS, Meilleur F, Lo Leggio L IUCrJ. 2022 Aug 17;9(Pt 5):666-681. doi: 10.1107/S2052252522007175. eCollection, 2022 Sep 1. PMID:36071795^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.