Thermostabilization of a thermophilic 1,4-α-glucan branching enzyme through C-terminal truncation.
Thermophilic proteins are useful for the detailed investigation of thermostability because they function efficiently at high temperatures. Comparison of the amino acid sequences and three-dimensional structures of mesophilic and thermophilic 1,4-α-glucan branching enzymes (GBEs) shows that the amino acid sequence of the last 26 residues at the C-terminal end of the GBE from Geobacillus thermoglucosidans STB02 (GBEGt, GenBank accession no. KJ660983) are not conserved, and that their 3-dimensional structure is flexible. These residues appear to be modified based upon a balance between flexibility and rigidity that is related to thermostability. In this study, a truncated mutant of GBEGt made by removing the last 26 residues from its C-terminal end was found to have increased thermostability and solubility, compared with the wild-type enzyme. Additionally, truncation of a portion of the C-terminus resulted in a decrease in aqueous stability. The circular dichroism spectra of GBEGt and GBEGtΔC were also found to be different. These results suggest that deletion of flexible residues at the C-terminal end of GBEGt, which are located on the surface of the enzyme, enhances the thermostability of the enzyme without significantly compromising its enzymatic activity.
['Ban|Xiaofeng|X|', 'Liu|Yiting|Y|', 'Zhang|Yuzhu|Y|', 'Gu|Zhengbiao|Z|', 'Li|Caiming|C|', 'Cheng|Li|L|', 'Hong|Yan|Y|', 'Dhoble|Abhishek S|AS|', 'Li|Zhaofeng|Z|']
D015061:1,4-alpha-Glucan Branching Enzyme D000595:Amino Acid Sequence D002942:Circular Dichroism D017124:Conserved Sequence D004795:Enzyme Stability D007700:Kinetics D011489:Protein Denaturation D058767:Protein Unfolding D012995:Solubility D013696:Temperature
1,4-α-Glucan branching enzyme Thermostability Truncation parts of C-terminus