6q29

Publication Abstract from PubMed

The multi-copper oxidase from the hyper-thermophilic bacteria Thermus thermophilus (Tth-MCO), has been previously characterized and described as an example of a laccase with low catalytic properties, especially when it is compared with the activity of fungal laccases, but it is active at high temperatures. Structurally, Tth-MCO has a unique feature: a beta-hairpin near the T1Cu site, which is not present in any other laccases deposited at the PDB. This beta-hairpin has an expected crystallographic behavior in solvent-exposed areas of a crystallized protein: lack of electron density, high B-values and several crystalline contacts with neighboring crystallographic copies; however, its dynamical behavior in solution and its biological implications have not been described. Here, we describe four new Tth-MCO crystallographic structures, and the beta-hairpin behavior has been analyzed by molecular dynamics simulations, considering the effect of pH and temperature. The beta-hairpin new crystallographic conformations described here, together with their dynamics, were used to understand the pH-restrained laccase activity of Tth-MCO against substrates as syringaldazine. Remarkably, there are insertions in laccases from Thermus and Meiothermus genus, sharing the same position and a methionine-rich composition of the Tth-MCO beta-hairpin. This unique high methionine content of the Tth-MCO beta-hairpin is responsible to coordinate, Ag(+1) and Hg(+1) in oxidative conditions, but Cu(+1) and Cu(+2) are not coordinated in crystallographic experiments, regardless of the redox conditions; however, Ag(+1) addition does not affect Tth-MCO laccase activity against syringaldazine. Here, we propose that the pH-dependent beta-hairpin dynamical behavior could explain, at least in part, the inefficient laccase activity displayed by Tth-MCO in acidic pH values.

The beta-hairpin from the Thermus thermophilus HB27 laccase works as a pH-dependent switch to regulate laccase activity.,Miranda-Blancas R, Avelar M, Rodriguez-Arteaga A, Sinicropi A, Rudino-Pinera E J Struct Biol. 2021 Jun;213(2):107740. doi: 10.1016/j.jsb.2021.107740. Epub 2021 , May 5. PMID:33962016^[1]

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