Figure 1

Amino acid sequence alignment of E. coli β-galactosidase with the K. lactis and A. niger β-galactosidase. Multiple sequence alignment of Escherichia coli β-galactosidase (ECLACZ), Kluyveromyces lactis β-galactosidase (KLLAC4) and Aspergillus niger β-galacatosidase (ANLACA). "*" means that the residues in that column are identical in all sequences in the alignment. ":" means that conserved substitutions have been observed. "." means that semi-conserved substitutions are observed. Acid (blue colour) and basic (red colour) amino acids of K. lactis and A. niger β-galactosidase are marked. The coloured bar below the E. coli β-galactosidase represents the five different domains structurally determined in the protein (Domain 1: green; Domain 2: yellow; Domain 3: red; Domain 4: light blue; Domain 5: dark blue). The secondary structure of E. coli β-galactosidase was obtained from the Protein Data Bank [42]. The localization of the restriction sites Bam HI (residues underlined and pink) and Kpn I (residues underlined and blue) are indicated. The conserved residues in E. coli β-galactosidase and K. lactis β-galactosidase important for catalytic function in E. coli β-galactosidase are shown in green. The residues of A. niger signal sequence are in yellow and underlined.