The variable structural flexibility of the<i> Bacillus circulans</i> β-galactosidase isoforms determines their unique functionalities
| Authors | |
|---|---|
| Year of publication | 2024 |
| Type | Article in Periodical |
| Magazine / Source | Structure |
| MU Faculty or unit | |
| Citation | |
| web | https://www.cell.com/structure/abstract/S0969-2126(24)00374-5?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0969212624003745%3Fshowall%3Dtrue |
| Doi | http://dx.doi.org/10.1016/j.str.2024.09.005 |
| Keywords | CRYO-EMOLIGOSACCHARIDE PRODUCTION; REFINEMENT; MECHANISMS; CLONING; SYSTEM; MODEL; GENE |
| Description | beta-Galactosidase from Bacillus circulans ATCC 31382 (BgaD) is a biotechnologically important enzyme for the synthesis of beta-galactooligosaccharides (GOS). Among its four isoforms, isoform A (BgaD-A) has distinct synthetic properties. Here, we present cryoelectron microscopy (cryo-EM) structures of BgaD-A and compare them with the known X-ray crystal structure of isoform D (BgaD-D), revealing substantial structural divergences between the two isoforms. In contrast to BgaD-D, BgaD-A features a flexible Big-4 domain and another enigmatic domain. The newly identified flexible region in BgaD-A is termed as "barrier domain 8," and serves as a barricade, obstructing the access of longer oligosaccharide substrates into the active site of BgaD-A. The transgalactosylation reactions catalyzed by both isoforms revealed that BgaD-A has a higher selectivity than BgaD-D in the earlier stages of the reaction and is prevailingly directed to shorter galactooligosaccharides. This study improves our understanding of the structural determinants governing R-galactosidase catalysis, with implications for tailored GOS production. |
| Related projects: |