The linker region plays a key role in the adaptation to cold of the cellulase from an Antarctic bacterium.

• Published in: Biochemical Journal
• Main Authors: Sonan, Guillaume K, Receveur-Brechot, Véronique, Duez, Colette, Aghajari, Nushin, Czjzek, Mirjam, Haser, Richard, Gerday, Charles
• Other Authors: Interactions et Modulateurs de Réponses (IMR), Centre National de la Recherche Scientifique (CNRS), Centre d’Ingénierie des Protéines Université de Liège = Centre for Protein Engineering University of Liège (CIP), Université de Liège, Résonance Magnétique Nucléaire des Biomolécules, Institut Pasteur Paris (IP)-Centre National de la Recherche Scientifique (CNRS), Institut de biologie et chimie des protéines Lyon (IBCP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: MESH: Acclimatization; MESH: Catalysis; MESH: Cellulase; MESH: Cold Temperature; MESH: Enzyme Stability; MESH: Mutation; MESH: Protein Conformation; MESH: Pseudoalteromonas; [SDV.BBM]Life Sciences [q-bio]/Biochemistry; Molecular Biology; Antarctic; The Antarctic; Antarc*
• Online Access: https://hal.science/hal-00473856; https://doi.org/10.1042/BJ20070640

International audience The psychrophilic cellulase, Cel5G, from the Antarctic bacterium Pseudoalteromonas haloplanktis is composed of a catalytic module (CM) joined to a carbohydrate-binding module (CBM) by an unusually long, extended and flexible linker region (LR) containing three loops closed by three disulfide bridges. To evaluate the possible role of this region in cold adaptation, the LR was sequentially shortened by protein engineering, successively deleting one and two loops of this module, whereas the last disulfide bridge was also suppressed by replacing the last two cysteine residue by two alanine residues. The kinetic and thermodynamic properties of the mutants were compared with those of the full-length enzyme, and also with those of the cold-adapted CM alone and with those of the homologous mesophilic enzyme, Cel5A, from Erwinia chrysanthemi. The thermostability of the mutated enzymes as well as their relative flexibility were evaluated by differential scanning calorimetry and fluorescence quenching respectively. The topology of the structure of the shortest mutant was determined by SAXS (small-angle X-ray scattering). The data indicate that the sequential shortening of the LR induces a regular decrease of the specific activity towards macromolecular substrates, reduces the relative flexibility and concomitantly increases the thermostability of the shortened enzymes. This demonstrates that the long LR of the full-length enzyme favours the catalytic efficiency at low and moderate temperatures by rendering the structure not only less compact, but also less stable, and plays a crucial role in the adaptation to cold of this cellulolytic enzyme.