Download MendeleyStructure and Carbohydrate Recognition by the Nonmitogenic Lectin Horcolin.
Narayanan, V., Bobbili, K.B., Sivaji, N., Jayaprakash, N.G., Suguna, K., Surolia, A., Sekhar, A.(2022) Biochemistry 61: 464-478
- PubMed: 35225598
- DOI: https://doi.org/10.1021/acs.biochem.1c00778
- Primary Citation of Related Structures:
7V4S, 7V4Z - PubMed Abstract:
Lectins are sugar-binding proteins that have shown considerable promise as antiviral agents because of their ability to interact with envelope glycoproteins present on the surface of viruses such as HIV-1. However, their therapeutic potential has been compromised by their mitogenicity that stimulates uncontrolled division of T-lymphocytes. Horcolin, a member of the jacalin family of lectins, tightly binds the HIV-1 envelope glycoprotein gp120 and neutralizes HIV-1 particles but is nonmitogenic. In this report, we combine X-ray crystallography and NMR spectroscopy to obtain atomic-resolution insights into the structure of horcolin and the molecular basis for its carbohydrate recognition. Each protomer of the horcolin dimer adopts a canonical β-prism I fold with three Greek key motifs and carries two carbohydrate-binding sites. The carbohydrate molecule binds in a negatively charged pocket and is stabilized by backbone and side chain hydrogen bonds to conserved residues in the ligand-binding loop. NMR titrations reveal a two-site binding mode and equilibrium dissociation constants for the two binding sites determined from two-dimensional (2D) lineshape modeling are 4-fold different. Single-binding-site variants of horcolin confirm the dichotomy in binding sites and suggest that there is allosteric communication between the two sites. An analysis of the horcolin structure shows a network of hydrogen bonds linking the two carbohydrate-binding sites directly and through a secondary binding site, and this coupling between the two sites is expected to assume importance in the interaction of horcolin with high-mannose glycans found on viral envelope glycoproteins.
Organizational Affiliation:
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
