The variable structural flexibility of the Bacillus circulans β-galactosidase isoforms determines their unique functionalities
Jazyk angličtina Země Spojené státy americké Médium print-electronic
Typ dokumentu časopisecké články
PubMed
39353423
DOI
10.1016/j.str.2024.09.005
PII: S0969-2126(24)00374-5
Knihovny.cz E-zdroje
- Klíčová slova
- cryo-EM, crystal structure, galactooligosaccharide, galactosidase, structural flexibility, substrate specificity, transgalactosylation,
- MeSH
- Bacillus * enzymologie MeSH
- bakteriální proteiny chemie metabolismus MeSH
- beta-galaktosidasa * chemie metabolismus genetika MeSH
- elektronová kryomikroskopie * MeSH
- izoenzymy chemie metabolismus MeSH
- katalytická doména * MeSH
- krystalografie rentgenová MeSH
- molekulární modely * MeSH
- oligosacharidy metabolismus chemie MeSH
- protein - isoformy chemie metabolismus MeSH
- substrátová specifita MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- bakteriální proteiny MeSH
- beta-galaktosidasa * MeSH
- izoenzymy MeSH
- oligosacharidy MeSH
- protein - isoformy MeSH
β-Galactosidase from Bacillus circulans ATCC 31382 (BgaD) is a biotechnologically important enzyme for the synthesis of β-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 β-galactosidase catalysis, with implications for tailored GOS production.
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