FIG. 2.

Sequence comparison and assignment of secondary structure. The peptide sequence of PalI of Klebsiella sp. strain LX3 (K. si) is compared with the sequences of the thermolabile OGL of B. cereus ATCC 7064 (B. ce) (accession no. P21332) and the thermostable OGL of B. thermoglucosidasius KP1006 (B. th) (accession no. P29094). The secondary structural features, i.e., α (helix) and β (sheet), of B. cereus OGL, based on crystal structural analysis (11), are indicated above the sequence. The predicted secondary structural regions of PalI are underlined and labeled at the bottom (H, α-helix; E, β-sheet). The selection marker for the α-amylase family, QPDLN, is indicated by double lines. The potential amino acid residues for proline substitution are shown in boldface, and the two mutated residues, R³¹⁰ and E⁴⁹⁸, are indicated by ♠. The crucial invariant residues (D²⁴¹, E²⁹⁵, D³⁶⁹, H¹⁴⁵, and H³⁶⁸ in PalI) conserved in α-amylase and glucosyltransferase are indicated by +. Boxes I to IV show the regions containing the five essential residues.