6H0H

The ABC transporter associated binding protein from B. animalis subsp. lactis Bl-04 in complex with beta-1,6-galactobiose

Summary for 6H0H

• Entry DOI: 10.2210/pdb6h0h/pdb
• Descriptor: Probable solute binding protein of ABC transporter system for sugars, beta-D-galactopyranose-(1-6)-beta-D-galactopyranose, alpha-D-galactopyranose, ... (7 entities in total)
• Functional Keywords: complex, abc transporter, galactobiose, sugar binding protein
• Biological source: Bifidobacterium animalis subsp. lactis Bl-04
• Total number of polymer chains: 2
• Total formula weight: 94834.42

Authors

Fredslund, F.,Lo Leggio, L. (deposition date: 2018-07-09, release date: 2019-06-19, Last modification date: 2024-05-15)

Primary citation

Theilmann, M.C.,Fredslund, F.,Svensson, B.,Lo Leggio, L.,Abou Hachem, M.
Substrate preference of an ABC importer corresponds to selective growth on beta-(1,6)-galactosides inBifidobacterium animalissubsp.lactis.
J.Biol.Chem., 294:11701-11711, 2019

PubMed Abstract: Bifidobacteria are exposed to substantial amounts of dietary β-galactosides. Distinctive preferences for growth on different β-galactosides are observed within members, but the basis of these preferences remains unclear. We previously described the first β-(1,6)/(1,3)-galactosidase from subsp. Bl-04. This enzyme is relatively promiscuous, exhibiting only 5-fold higher efficiency on the preferred β-(1,6)-galactobiose than the β-(1,4) isomer. Here, we characterize the solute-binding protein (6GBP) that governs the specificity of the ABC transporter encoded by the same β-galactoside utilization locus. We observed that although 6GBP recognizes both β-(1,6)- and β-(1,4)-galactobiose, 6GBP has a 1630-fold higher selectivity for the former, reflected in dramatic differences in growth, with several hours lag on less preferred β-(1,4)- and β-(1,3)-galactobiose. Experiments performed in the presence of varying proportions of β-(1,4)/β-(1,6)-galactobioses indicated that the preferred substrate was preferentially depleted from the culture supernatant. This established that the poor growth on the nonpreferred β-(1,4) was due to inefficient uptake. We solved the structure of 6GBP in complex with β-(1,6)-galactobiose at 1.39 Å resolution, revealing the structural basis of this strict selectivity. Moreover, we observed a close evolutionary relationship with the human milk disaccharide lacto--biose-binding protein from , indicating that the recognition of the nonreducing galactosyl is essentially conserved, whereas the adjacent position is diversified to fit different glycosidic linkages and monosaccharide residues. These findings indicate that oligosaccharide uptake has a pivotal role in governing selectivity for distinct growth substrates and have uncovered evolutionary trajectories that shape the diversification of sugar uptake proteins within .

PubMed: 31186348
DOI: 10.1074/jbc.RA119.008843

Experimental method

X-RAY DIFFRACTION (1.39 Å)