The impact of glycosylation on the conformational ensembles of β-, δ-, and γ-sarcoglycans.

Glycosylation is a pivotal post-translational modification that influences protein folding, stability, and interactions with direct implications for muscular dystrophy pathogenesis and emerging gene therapies. Sarcoglycans (SGs), β, δ, γ, and α subunits of the dystrophin-glycoprotein complex (DGC), contain essential N-linked glycosylation sites, and mutations disrupt glycan attachment, destabilize the complex, and cause limb-girdle muscular dystrophy. However, the structural consequences of SG glycosylation remain poorly defined due to the absence of experimental SG complex structures. Here, we use homology modeling, AlphaFold predictions, and all-atom molecular-dynamics simulations to probe how N-linked glycans reshape the conformational ensembles of β-, δ-, and γ-SG monomers and the β-δ-γ heterotrimer core. We find that glycosylation increases flexibility and conformational heterogeneity in isolated monomers but reinforces a compact, stabilized architecture in the heterotrimer. Contact-map and clustering analyses show that glycans redistribute local residue interactions while preserving global trimer organization, suggesting a context-dependent role in destabilizing monomers yet reinforcing complex stability. These findings provide the first atomistic insight into how glycosylation primes SGs for assembly and may explain why mutations at glycosylation sites disrupt complex integrity and drive muscular dystrophy phenotypes.