New ligand-binding sites identified in the crystal structures of β-lactoglobulin complexes with desipramine

Joanna I. Loch, Jakub Barciszewski, Joanna Sliwiak, Piotr Bonarek, Paulina Wrobel, Kinga Pokrywka, Ivan G. Shabalin, Wladek Minor, Mariusz Jaskolski, Krzysztof Lewinski

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The homodimeric β-lactoglobulin belongs to the lipocalin family of proteins that transport a wide range of hydrophobic molecules and can be modified by mutagenesis to develop specificity for novel groups of ligands. In this work, new lactoglobulin variants, FAF (I56F/L39A/M107F) and FAW (I56F/L39A/M107W), were produced and their interactions with the tricyclic drug desipramine (DSM) were studied using X-ray crystallography, calorimetry (ITC) and circular dichroism (CD). The ITC and CD data showed micromolar affinity of the mutants for DSM and interactions according to the classical one-site binding model. However, the crystal structures unambiguously showed that the FAF and FAW dimers are capable of binding DSM not only inside the β-barrel as expected, but also at the dimer interface and at the entrance to the binding pocket. The presented high-resolution crystal structures therefore provide important evidence of the existence of alternative ligand-binding sites in the β-lactoglobulin molecule. Analysis of the crystal structures highlighted the importance of shape complementarity for ligand recognition and selectivity. The binding sites identified in the crystal structures of the FAF-DSM and FAW-DSM complexes together with data from the existing literature are used to establish a systematic classification of the ligand-binding sites in the β-lactoglobulin molecule.

Original languageEnglish
Pages (from-to)386-398
Number of pages13
JournalIUCrJ
Volume9
DOIs
StatePublished - 1 May 2022
Externally publishedYes

Keywords

  • desipramine
  • ligand-binding sites
  • β-lactoglobulin

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