Oligomerization as a strategy for cold adaptation: Structure and dynamics of the GH1 β-glucosidase from Exiguobacterium antarcticum B7

• Published in: Scientific reports Vol. 6; no. 1; p. 23776
• Main Authors: Zanphorlin, Leticia Maria, de Giuseppe, Priscila Oliveira, Honorato, Rodrigo Vargas, Tonoli, Celisa Caldana Costa, Fattori, Juliana, Crespim, Elaine, de Oliveira, Paulo Sergio Lopes, Ruller, Roberto, Murakami, Mario Tyago
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 31-03-2016; Nature Publishing Group
• Subjects: 631/45/607/1164; 631/535/1266; 82/80; 82/83; Adaptation, Physiological - genetics; Aquatic Organisms; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; beta-Glucosidase - chemistry; beta-Glucosidase - genetics; beta-Glucosidase - metabolism; Cloning, Molecular; Cold Temperature; Crystallography, X-Ray; Enzyme Stability; Escherichia coli - genetics; Escherichia coli - metabolism; Firmicutes - classification; Firmicutes - enzymology; Firmicutes - genetics; Gene Expression; Humanities and Social Sciences; Hydrophobic and Hydrophilic Interactions; Kinetics; Molecular Dynamics Simulation; multidisciplinary; Phylogeny; Protein Domains; Protein Multimerization; Protein Structure, Secondary; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Science; Science (multidisciplinary); Thermodynamics
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep23776

Psychrophilic enzymes evolved from a plethora of structural scaffolds via multiple molecular pathways. Elucidating their adaptive strategies is instrumental to understand how life can thrive in cold ecosystems and to tailor enzymes for biotechnological applications at low temperatures. In this work, we used X-ray crystallography,
in solution
studies and molecular dynamics simulations to reveal the structural basis for cold adaptation of the GH1 β-glucosidase from
Exiguobacterium antarcticum
B7. We discovered that the selective pressure of low temperatures favored mutations that redesigned the protein surface, reduced the number of salt bridges, exposed more hydrophobic regions to the solvent and gave rise to a tetrameric arrangement not found in mesophilic and thermophilic homologues. As a result, some solvent-exposed regions became more flexible in the cold-adapted tetramer, likely contributing to enhance enzymatic activity at cold environments. The tetramer stabilizes the native conformation of the enzyme, leading to a 10-fold higher activity compared to the disassembled monomers. According to phylogenetic analysis, diverse adaptive strategies to cold environments emerged in the GH1 family, being tetramerization an alternative, not a rule. These findings reveal a novel strategy for enzyme cold adaptation and provide a framework for the semi-rational engineering of β-glucosidases aiming at cold industrial processes.