Cloning, characterization, and computer- aided evolution of a
thermostable laccase of the DUF152 family from Klebsiella michiganensis
Abstract
Bacterial laccases exhibit relatively high optimal reaction temperatures
and possess a broad substrate spectrum, thereby expanding the range of
potential applications for laccase enzymes. This study aims to
investigate the molecular evolution of bacterial laccases using
computational simulation tools such as AlphaFold2, Metal3D,
AutoDockVina, and Rosetta. We isolated a bacterium with laccase
activities from fecal samples from a Hermann´s tortoise ( Testudo
hermanni), identified it as Klebsiella michiganensis using 16S
rRNA sequencing and nanopore genome sequencing, and then identified a
sequence encoding a laccase with a predicted molecular weight of
approximately 27.5 kDa. Expression of the corresponding, chemically
synthesized DNA fragment resulted in the isolation of an active laccase.
The enzyme showed considerable thermostability, retaining 21% of its
activity after boiling for 30 min. Using state-of-the-art information
technology and machine learning techniques, we conducted simulations on
this sequence, predicted its copper-ion binding sites, and validated
these predictions through site-directed mutagenesis and expression.
Subsequently, we performed computer-aided evolution studies on this
sequence and found that 90% of the results from simulations exhibited
improved performance. In summary, this study not only revealed a novel
laccase but also demonstrated an efficient approach for advancing
research on the molecular evolution of bacterial laccases using
cutting-edge machine learning, next-generation sequencing, traditional
bioinformatics approaches, and laboratory techniques, providing an
effective strategy for discovering and design new bacterial laccases.