Structural and thermodynamic insights into -1,2-glucooligosaccharide capture by a solute-binding protein in Listeria innocua

Koichi Abe, Naoki Sunagawa, Tohru Terada, Yuta Takahashi, Takatoshi Arakawa, Kiyohiko Igarashi, Masahiro Samejima, Hiroyuki Nakai, Hayao Taguchi, Masahiro Nakajima, Shinya Fushinobu

Research output: Contribution to journalArticleScientificpeer-review

10 Citations (Scopus)

Abstract

β-1,2-Glucans are bacterial carbohydrates that exist in cyclic or linear forms and play an important role in infections and symbioses involving Gram-negative bacteria. Although several β-1,2-glucan–associated enzymes have been characterized, little is known about how β-1,2-glucan and its shorter oligosaccharides (Sopns) are captured and imported into the bacterial cell. Here, we report the biochemical and structural characteristics of the Sopn-binding protein (SO-BP, Lin1841) associated with the ATP-binding cassette (ABC) transporter from the Gram-positive bacterium Listeria innocua. Calorimetric analysis revealed that SO-BP specifically binds to Sopns with a degree of polymerization of 3 or more, with Kd values in the micromolar range. The crystal structures of SO-BP in an unliganded open form and in closed complexes with tri-, tetra-, and pentaoligosaccharides (Sop3–5) were determined to a maximum resolution of 1.6 Å. The binding site displayed shape complementarity to Sopn, which adopted a zigzag conformation. We noted that water-mediated hydrogen bonds and stacking interactions play a pivotal role in the recognition of Sop3–5 by SO-BP, consistent with its binding thermodynamics. Computational free-energy calculations and a mutational analysis confirmed that interactions with the third glucose moiety of Sopns are significantly responsible for ligand binding. A reduction in unfavorable changes in binding entropy that were in proportion to the lengths of the Sopns was explained by conformational entropy changes. Phylogenetic and sequence analyses indicated that SO-BP ABC transporter homologs, glycoside hydrolases, and other related proteins are co-localized in the genomes of several bacteria. This study may improve our understanding of bacterial β-1,2-glucan metabolism and promote the discovery of unidentified β-1,2-glucan–associated proteins.

Original languageEnglish
Pages (from-to)8812-8828
Number of pages17
JournalJournal of Biological Chemistry
Volume293
Issue number23
DOIs
Publication statusPublished - 8 Jun 2018
MoE publication typeA1 Journal article-refereed

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    Abe, K., Sunagawa, N., Terada, T., Takahashi, Y., Arakawa, T., Igarashi, K., Samejima, M., Nakai, H., Taguchi, H., Nakajima, M., & Fushinobu, S. (2018). Structural and thermodynamic insights into -1,2-glucooligosaccharide capture by a solute-binding protein in Listeria innocua. Journal of Biological Chemistry, 293(23), 8812-8828. https://doi.org/10.1074/jbc.RA117.001536