X-ray Crystallography of a Novel Thermostable .BETA.-Galactosidase from Thermus thermophilus A4, and Its Complex Structure with Galactose.

Cold-active β-Galactosidase from Arthrobacter sp. C2-2 Forms Compact 660kDa Hexamers: Crystal Structure at 1.9Å Resolution

“…(PDB codes 1TG7 and 1XC6, monomer); 27 GH family 42, b-galactosidase from Thermus thermophilus A4 (PDB codes 1KWG and 1KWK, trimer). 28 Hexameric cage-like packing of b-galactosidase C221-b-Gal found in the reported structure is the first supramolecular arrangement of this type known in the galactosidase superfamily. The structure of one monomer of C221-b-Gal resembles that of E. coli b-galactosidase from the same GH family 2 (sequence identity 33%).…”

Crystal Structures of β-Galactosidase from Penicillium sp. and its Complex with Galactose

“…Each A4-b-gal monomer is composed of only three domains, a TIM barrel, an a/b fold and a b fold domain. 8 The TIM barrel is more regular than that seen in either Psp-b-gal or Ec-b-gal. Neither of the latter two domains bare any resemblance to the non-catalytic domains observed in Psp-b-gal.…”

“…[16][17][18] The only other b-galactosidase of known crystal structure is that from Thermus thermophilus (A4-b-gal), a member of GHF-42. 8 Ec-b-gal forms a 464 kDa homotetramer in solution, whereas A4-b-gal is a trimer.…”

“…[1][2][3][4][5][6][7] b-Galactosidases are used for the hydrolysis of lactose in dairy products, such as milk and cheese whey, and thermostable b-galactosidases recently attracted special interest due to their potential usefulness in the industrial processing of lactosecontaining products. 8 Furthermore, b-galactosidases have also been used as a tool in molecular biology due to the fairly strict specificity towards galactosyl bonds but not to a wide variety of aglycons. This feature allows the use of simple, colorimetric assays based on substrates such as p-nitrophenyl-b-D-galactopyranoside (PNPG) and b-D-galactopyranoside with chromogenic aglycons (XGal).…”