Structural flexibility of human α-dystroglycan.

Area of Science:

• Biochemistry
• Structural Biology
• Glycobiology

Background:

• Dystroglycan (DG) is vital for the dystrophin-associated glycoprotein complex, with its α-subunit (α-DG) requiring post-translational glycosylation for function.
• The enzyme like-acetylglucosaminyltransferase (LARGE) is essential for α-DG maturation and laminin binding.
• Previous structural analysis of murine α-DG N-terminus (α-DG-Nt) and a LARGE-interaction mutant left interaction details elusive.

Purpose of the Study:

• To determine the crystal structure of wild-type human α-DG-Nt.
• To compare human and murine α-DG-Nt structures in solution.
• To investigate the structural flexibility and conformational ensembles of α-DG-Nt.

Main Methods:

• X-ray crystallography for human α-DG-Nt structure determination.
• Small-angle X-ray scattering (SAXS) to analyze solution structures and conformations.
• Biochemical and biophysical experiments to assess protein stability and interdomain flexibility.

Main Results:

• The crystal structure of human α-DG-Nt was determined, validating the murine model.
• SAXS revealed two distinct conformational ensembles in solution for both human and murine α-DG-Nt.
• Comparative analysis showed conserved interdomain flexibility and conformer distribution between human and murine orthologs.

Conclusions:

• α-DG-Nt exhibits significant molecular plasticity in solution, existing in at least two conformations.
• This inherent flexibility is conserved across species and likely plays a key role in functional interactions.
• Understanding α-DG-Nt plasticity is essential for comprehending its role in cellular processes and disease pathogenesis.