7V4S image
Entry Detail
PDB ID:
7V4S
Title:
Horcolin complex with methyl-alpha-mannose
Biological Source:
PDB Version:
Deposition Date:
2021-08-14
Release Date:
2022-03-09
Method Details:
Experimental Method:
Resolution:
1.20 Å
R-Value Free:
0.23
R-Value Work:
0.20
Space Group:
P 31 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Horcolin
Chain IDs:A
Chain Length:146
Number of Molecules:1
Biological Source:Hordeum vulgare
Ligand Molecules
Primary Citation
Structure and Carbohydrate Recognition by the Nonmitogenic Lectin Horcolin.
Biochemistry 61 464 478 (2022)
PMID: 35225598 DOI: 10.1021/acs.biochem.1c00778

Abstact

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.

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