Figure 1.
Comparison of amino acid sequences of GH1 family proteins possessing 6Pβ-gal, 6Pβ-glc, and dual 6Pβ-gal/6Pβ-glc activity. 4PBG, LacG from L. lactis subsp. lactis (P11546) and 4GPN from S. mutans ATCC 700610 (Q8DT00) possessed PDB structures and were previously used as models for 6Pβ-gal and 6Pβ-glc GH1 proteins, respectively.27 The alignment includes Lp_3525 from L. plantarum WCFS1 (CCC80491), Pbg1 (BAA20086) and Pbg2 (BAA25004) from L. gasseri, and proteins described to possess dual 6Pβ-gal/6Pβ-glc activity, such as BlBglC from B. licheniformis (UPI000043D040), GK3214 from G. kaustophilus HTA426 (Q5KUY7), and Gan1D from Geobacillus stearothermophilus (W8QF82). Residues that are identical (*), conserved (:), or semiconserved (·) in all sequences are indicated. Dashes indicate gaps introduced to maximize similarities. The conserved catalytic acid/base and nucleophilic Glu residues are marked in white letters and highlighted in navy blue. Residues conserved in the particular activity in which it belongs are highlighted in yellow for dual 6Pβ-gal/6Pβ-glc, green for 6Pβ-gal, and blue for 6Pβ-glc.27 Residues described as specific for one activity but conserved in the three activities studied are marked in white letters and highlighted in pink.27 The residues Asn/Ser and Trp/Ala which defined the preference for 6P-β-Gal or 6P-β-Glc substrates29 are marked in green boxes and with a green star. The long extra C-terminal segment present in 6Pβ-glc is marked in a blue box. The conserved lid motif present in 6Pβ-gal that blocks the entrance to the active site is marked in a red box.