Structures of the psychrophilic Alteromonas haloplanctis α-amylase give insights into cold adaptation at a molecular level

• Published in: Structure (London) 1998-12, Vol.6 (12), p.1503-1516
• Main Authors: Aghajari, Nushin, Feller, Georges, Gerday, Charles, Haser, Richard
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological; alpha-Amylases - chemistry; alpha-Amylases - metabolism; Amino Acid Sequence; Amino Acids - chemistry; Binding Sites; Biochemistry, Molecular Biology; Calcium - metabolism; Chlorides - metabolism; cold adaptation; Cold Temperature; Crystallography, X-Ray; Disulfides - chemistry; family 13 glycosyl hydrolase; Gram-Negative Aerobic Bacteria - enzymology; Gram-Negative Aerobic Bacteria - physiology; Hydrogen Bonding; Life Sciences; Models, Molecular; Molecular Sequence Data; Protein Structure, Secondary; psychrophiles; Recombinant Proteins - chemistry; Sequence Homology, Amino Acid; Surface Properties; X-ray structure
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/S0969-2126(98)00149-X

Background: Enzymes from psychrophilic (cold-adapted) microorganisms operate at temperatures close to 0°C, where the activity of their mesophilic and thermophilic counterparts is drastically reduced. It has generally been assumed that thermophily is associated with rigid proteins, whereas psychrophilic enzymes have a tendency to be more flexible. Results: Insights into the cold adaptation of proteins are gained on the basis of a psychrophilic protein's molecular structure. To this end, we have determined the structure of the recombinant form of a psychrophilic α-amylase from Alteromonas haloplanctis at 2.4 å resolution. We have compared this with the structure of the wild-type enzyme, recently solved at 2.0 å resolution, and with available structures of their mesophilic counterparts. These comparative studies have enabled us to identify possible determinants of cold adaptation. Conclusions: We propose that an increased resilience of the molecular surface and a less rigid protein core, with less interdomain interactions, are determining factors of the conformational flexibility that allows efficient enzyme catalysis in cold environments.