Molecular characterization of the Thermomonospora curvata aglA gene encoding a thermotolerant #alpha#-1, 4-glucosidase

摘要

The cloning, sequencing and structural characterization of a gene encoding a thermostable #alpha#-1,4-glucosidase from Thermomonospora curvata is described. DNA sequence analysis revealed four open reading frames designated aglA, aglR, aglE and aglF. The aglA gene encodes a thermostable #alpha#-1,4-glucosidase from T. curvata and is situated between two genes, aglR and aglE. Genes aglA, aglE and aglF are transcribed in the same direction, while aglR is transcribed in the opposite direction. By comparing the amino acid sequence of the #alpha#-1,4-glucosidase from T. curvata with other #alpha#-glucanases, it appears that the enzyme is a member of the #alpha#-amylase family. The proteins of this family have an (#alpha#/#beta#)_8 barrel super secondary structure. The topology of the #alpha#-1,4-glucosidase was predicted by computer-assisted analysis. The topology of the secondary structures of the #alpha#-1,4-glucosidase resembles the structure of barley #alpha#-amylase, but the primary structure resembles most closely the oligo-1,6-glucosidase from Bacillus cereus. Putative catalytic residues (D221, E281, and D343) and calcium binding residues (N116, E179, D191, H224 or G225) are proposed.