Binding Sites for Oligosaccharide Repeats from Lactic Acid Bacteria Exopolysaccharides on Bovine β-Lactoglobulin Identified by NMR Spectroscopy

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

  • Johnny Birch
  • Sanaullah Khan
  • Mikkel Madsen
  • Christian Kjeldsen
  • Marie Sofie Møller
  • Emil G. P. Stender
  • Günther H. J. Peters
  • Jens Ø. Duus
  • Kragelund, Birthe Brandt
  • Birte Svensson

Lactic acid bacterial exopolysaccharides (EPS) are used in the food industry to improve the stability and rheological properties of fermented dairy products. β-Lactoglobulin (BLG), the dominant whey protein in bovine milk, is well known to bind small molecules such as fatty acids, vitamins, and flavors, and to interact with neutral and anionic polysaccharides used in food and pharmaceuticals. While sparse data are available on the affinity of EPS-milk protein interactions, structural information on BLG-EPS complexes, including the EPS binding sites, is completely lacking. Here, binding sites on BLG variant A (BLGA), for oligosaccharides prepared by mild acid hydrolysis of two EPS produced by Streptococcus thermophilus LY03 and Lactobacillus delbrueckii ssp. bulgaricus CNRZ 1187, respectively, are identified by NMR spectroscopy and supplemented by isothermal titration calorimetry (ITC) and molecular docking of complexes. Evidence of two binding sites (site 1 and site 2) on the surface of BLGA is achieved for both oligosaccharides (LY03-OS and 1187-OS) through NMR chemical shift perturbations, revealing multivalency of BLGA for EPS. The affinities of LY03-OS and 1187-OS for BLGA gave KD values in the mM range obtained by both NMR (pH 2.65) and ITC (pH 4.0). Molecular docking suggested that the BLGA and EPS complexes depend on hydrogen bonds and hydrophobic interactions. The findings provide insights into how BLGA engages structurally different EPS-derived oligosaccharides, which may facilitate the design of BLG-EPS complexation, of relevance for formulation of dairy products and improve understanding of BLGA coacervation.

OriginalsprogEngelsk
TidsskriftACS Omega
Vol/bind6
Udgave nummer13
Sider (fra-til)9039-9052
Antal sider14
ISSN2470-1343
DOI
StatusUdgivet - 2021

Bibliografisk note

Funding Information:
The project Associative interactions between EPS from lactic acid bacteria and milk proteins gaining insights deployable in the design of optimized food texture (HEXPIN) is supported by the Independent Research Fund Denmark Technology and Production Sciences (grant no. DFF–1335-00221). The oligosaccharides spectra were recorded at the NMR Center DTU, and the protein spectra were recorded at the Structural Biology and NMR Laboratory at BIO, UCPH, both supported by Villum Fonden. Some of the spectra were recorded at cOpenNMR, Department of Biology, UCPH, supported by the Novo Nordisk Foundation (#NNF18OC0032996). Novo Nordisk Foundation is thanked for funding by J.Ø.D and C.K. for grant no. 5371 and by B.S. for grant no. NNFOC0027616. J.B., M.M., and E.G.P.S. thank the Technical University of Denmark (DTU) for 1/3 PhD scholarships.

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