title: Crystal structures of a psychrophilic metalloprotease reveal new insights into catalysis by cold-adapted proteases.
abstract: Enzymes from psychrophilic organisms differ from their mesophilic counterparts in having a lower thermostability and a higher specific activity at low and moderate temperatures. It is in general accepted that psychrophilic enzymes are more flexible to allow easy accommodation and transformation of the substrates at low energy costs. Here, we report the structures of two crystal forms of the alkaline protease from an Antarctic Pseudomonas species (PAP), solved to 2.1- and 1.96-A resolution, respectively. Comparative studies of PAP structures with mesophilic counterparts show that the overall structures are similar but that the conformation of the substrate-free active site in PAP resembles that of the substrate-bound region of the mesophilic homolog, with both an active-site tyrosine and a substrate-binding loop displaying a conformation as in the substrate-bound form of the mesophilic proteases. Further, a region in the catalytic domain of PAP undergoes a conformational change with a loop movement as large as 13 A, induced by the binding of an extra calcium ion. Finally, the active site is more accessible due to deletions occurring in surrounding loop regions.
authors.affiliation: Institut de Biologie et Chimie des Protéines, UMR 5086, Laboratoire de Bio-Cristallographie, CNRS et Université Claude Bernard Lyon I, Lyon, France. n.aghajari@ibcp.fr
authors.forename: Nushin
authors.initials: N
authors.lastname: Aghajari
authors.forename: Filip
authors.initials: F
authors.lastname: Van Petegem
authors.forename: Vincent
authors.initials: V
authors.lastname: Villeret
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Chessa
authors.forename: Charles
authors.initials: C
authors.lastname: Gerday
authors.forename: Richard
authors.initials: R
authors.lastname: Haser
authors.forename: Jozef
authors.initials: J
authors.lastname: Van Beeumen
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002384:Catalysis; D020134:Catalytic Domain; D003080:Cold Temperature; D018360:Crystallography, X-Ray; D005453:Fluorescence; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008666:Metalloendopeptidases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; C038495:Pseudomonas serine proteinase; D012697:Serine Endopeptidases; D008666:Metalloendopeptidases; C095666:serralysin; D002118:Calcium