Structures of the psychrophilic Alteromonas haloplanctis alpha-amylase give insights into cold adaptation at a molecular level.
BACKGROUND
. Enzymes from psychrophilic (cold-adapted) microorganisms operate at temperatures close to 0 degreesC, 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 alpha-amylase from Alteromonas haloplanctis at 2.4 A resolution. We have compared this with the structure of the wild-type enzyme, recently solved at 2.0 A 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.
Aghajari
N
N
Institut de Biologie et Chimie des Protéines UPR 412, CNRS 7 Passage du Vercors 69367 Lyon cedex 07 France.
Feller
G
G
Gerday
C
C
Haser
R
R
D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003080:Cold Temperature; D018360:Crystallography, X-Ray; D004220:Disulfides / Q000737:chemistry; D006088:Gram-Negative Aerobic Bacteria / Q000201:enzymology* / Q000502:physiology; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013499:Surface Properties; D000516:alpha-Amylases / Q000737:chemistry* / Q000378:metabolism
D000596:Amino Acids; D002712:Chlorides; D004220:Disulfides; D011994:Recombinant Proteins; D000516:alpha-Amylases; D002118:Calcium