8SDB

Crystal Structure of E.Coli Branching Enzyme in complex with malto-octose

Summary for 8SDB

• Entry DOI: 10.2210/pdb8sdb/pdb
• Descriptor: 1,4-alpha-glucan branching enzyme GlgB, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, ... (7 entities in total)
• Functional Keywords: branching enzyme, starch, e. coli branching enzyme, sugar binding protein, transferase-carbohydrate complex, transferase/carbohydrate
• Biological source: Escherichia coli
• Total number of polymer chains: 4
• Total formula weight: 292761.19

Authors

Bingham, C.R.,Nayebi, H.,Fawaz, R.,Geiger, J.H. (deposition date: 2023-04-06, release date: 2023-07-12, Last modification date: 2023-08-16)

Primary citation

Fawaz, R.,Bingham, C.,Nayebi, H.,Chiou, J.,Gilbert, L.,Park, S.H.,Geiger, J.H.
The Structure of Maltooctaose-Bound Escherichia coli Branching Enzyme Suggests a Mechanism for Donor Chain Specificity.
Molecules, 28:-, 2023

PubMed Abstract: Glycogen is the primary storage polysaccharide in bacteria and animals. It is a glucose polymer linked by α-1,4 glucose linkages and branched via α-1,6-linkages, with the latter reaction catalyzed by branching enzymes. Both the length and dispensation of these branches are critical in defining the structure, density, and relative bioavailability of the storage polysaccharide. Key to this is the specificity of branching enzymes because they define branch length. Herein, we report the crystal structure of the maltooctaose-bound branching enzyme from the enterobacteria . The structure identifies three new malto-oligosaccharide binding sites and confirms oligosaccharide binding in seven others, bringing the total number of oligosaccharide binding sites to twelve. In addition, the structure shows distinctly different binding in previously identified site I, with a substantially longer glucan chain ordered in the binding site. Using the donor oligosaccharide chain-bound branching enzyme structure as a guide, binding site I was identified as the likely binding surface for the extended donor chains that the branching enzyme is known to transfer. Furthermore, the structure suggests that analogous loops in branching enzymes from a diversity of organisms are responsible for branch chain length specificity. Together, these results suggest a possible mechanism for transfer chain specificity involving some of these surface binding sites.

PubMed: 37298853
DOI: 10.3390/molecules28114377

Experimental method

X-RAY DIFFRACTION (3 Å)