Structural and Functional Analysis of an HBB Variant (p.Leu4Gln) in β-Thalassemia and Its Impact on Heme Binding Using Molecular Docking

Abstract

Background: β -thalassemia is an inherited hemoglobin disorder caused by mutations in the HBB gene. This study investigated the structural and functional effects of the HBB p.Leu4Gln mutation on β-globin and its interaction with heme.

Methodology: The pathogenic variant NC_000011.10:g.5227020A>T (p.Leu4Gln) was identified through UniProt and evaluated using MutationTaster. Wild-type and mutant β-globin structures were modeled with AlphaFold2, and protein–heme docking was performed using MOE.

Results: The mutant protein exhibited a less favorable docking score (−9.8716 kcal/mol) than the wild type (−10.6160 kcal/mol) and a higher RMSD value (1.8171 vs. 1.2387 Å), indicating reduced binding affinity and stability. Interaction analysis revealed the formation of a metal coordination bond and a novel π-H interaction with His64 in the mutant complex, suggesting alteration of the heme-binding pocket.

Conclusion: The p.Leu4Gln mutation disrupts heme binding and alters the structural integrity of β-globin, potentially contributing to impaired hemoglobin function in β-thalassemia. These findings provide molecular insights into disease pathogenesis and potential therapeutic targets.