Cold-active beta-galactosidase from Arthrobacter sp. C2-2 forms compact 660 kDa hexamers: crystal structure at 1.9A resolution.
The X-ray structure of cold-active beta-galactosidase (isoenzyme C-2-2-1) from an Antarctic bacterium Arthrobacter sp. C2-2 was solved at 1.9A resolution. The enzyme forms 660 kDa hexamers with active sites opened to the central cavity of the hexamer and connected by eight channels with exterior solvent. To our best knowledge, this is the first cold-active beta-galactosidase with known structure and also the first known beta-galactosidase structure in the form of compact hexamers. The hexamer organization regulates access of substrates and ligands to six active sites and this unique packing, present also in solution, raises questions about its purpose and function. This enzyme belongs to glycosyl hydrolase family 2, similarly to Escherichia coli beta-galactosidase, forming tetramers necessary for its enzymatic function. However, we discovered significant differences between these two enzymes affecting the ability of tetramer/hexamer formation and complementation of the active site. This structure reveals new insights into the cold-adaptation mechanisms of enzymatic pathways of extremophiles.
Skálová
Tereza
T
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, 1606 Praha 6, Czech Republic. skalova@imc.cas.cz
Dohnálek
Jan
J
Spiwok
Vojtech
V
Lipovová
Petra
P
Vondrácková
Eva
E
Petroková
Hana
H
Dusková
Jarmila
J
Strnad
Hynek
H
Králová
Blanka
B
Hasek
Jindrich
J
D000595:Amino Acid Sequence; D001173:Arthrobacter / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D003080:Cold Temperature; D018360:Crystallography, X-Ray; D006801:Humans; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment; D012997:Solvents / Q000737:chemistry; D001616:beta-Galactosidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D007477:Ions; D012997:Solvents; D001616:beta-Galactosidase