The severe dystroglycanopathy known as a form of limb-girdle muscular dystrophy (LGMD2P) is an autosomal recessive disease caused by the point mutation T192M in α- dystroglycan. Functional expression analysis in vitro and in vivo indicated that the mutation was responsible for a decrease in posttranslational glycosylation of dystroglycan, eventually interfering with its extracellular-matrix receptor function and laminin binding in skeletal muscle and brain. The X-ray crystal structure of the missense variant T190M of the murine N-terminal domain of α-dystroglycan (50-313) has been determined, and showed an overall topology (Ig-like domain followed by a basket-shaped domain reminiscent of the small subunit ribosomal protein S6) very similar to that of the wild-type structure. The crystallographic analysis revealed a change of the conformation assumed by the highly flexible loop encompassing residues 159-180. Moreover, a solvent shell reorganization around Met190 affects the interaction between the B1-B5 anti-parallel strands forming part of the floor of the basket-shaped domain, with likely repercussions on the folding stability of the protein domain(s) and on the overall molecular flexibility. Chemical denaturation and limited proteolysis experiments point to a decreased stability of the T190M variant with respect to its wild-type counterpart. This mutation may render the entire L-shaped protein architecture less flexible. The overall reduced flexibility and stability may affect the functional properties of α-dystroglycan via negatively influencing its binding behavior to factors needed for dystroglycan maturation, and may lay the molecular basis of the T190M-driven primary dystroglycanopathy.

Bozzi, M., Cassetta, A., Covaceuszach, S., Bigotti, M., Bannister, S., Hubner, W., Sciandra, F., Lamba, D., Brancaccio, A., The Structure of the T190M Mutant of Murine α-Dystroglycan at High Resolution:Insight into the Molecular Basis of a Primary Dystroglycanopathy, <<PLOS ONE>>, 2015; 10 (5): N/A-N/A. [doi:10.1371/journal.pone.0124277] [http://hdl.handle.net/10807/72456]

The Structure of the T190M Mutant of Murine α-Dystroglycan at High Resolution: Insight into the Molecular Basis of a Primary Dystroglycanopathy

Bozzi, Manuela;Sciandra, Francesca;Brancaccio, Andrea
2015

Abstract

The severe dystroglycanopathy known as a form of limb-girdle muscular dystrophy (LGMD2P) is an autosomal recessive disease caused by the point mutation T192M in α- dystroglycan. Functional expression analysis in vitro and in vivo indicated that the mutation was responsible for a decrease in posttranslational glycosylation of dystroglycan, eventually interfering with its extracellular-matrix receptor function and laminin binding in skeletal muscle and brain. The X-ray crystal structure of the missense variant T190M of the murine N-terminal domain of α-dystroglycan (50-313) has been determined, and showed an overall topology (Ig-like domain followed by a basket-shaped domain reminiscent of the small subunit ribosomal protein S6) very similar to that of the wild-type structure. The crystallographic analysis revealed a change of the conformation assumed by the highly flexible loop encompassing residues 159-180. Moreover, a solvent shell reorganization around Met190 affects the interaction between the B1-B5 anti-parallel strands forming part of the floor of the basket-shaped domain, with likely repercussions on the folding stability of the protein domain(s) and on the overall molecular flexibility. Chemical denaturation and limited proteolysis experiments point to a decreased stability of the T190M variant with respect to its wild-type counterpart. This mutation may render the entire L-shaped protein architecture less flexible. The overall reduced flexibility and stability may affect the functional properties of α-dystroglycan via negatively influencing its binding behavior to factors needed for dystroglycan maturation, and may lay the molecular basis of the T190M-driven primary dystroglycanopathy.
2015
Inglese
Bozzi, M., Cassetta, A., Covaceuszach, S., Bigotti, M., Bannister, S., Hubner, W., Sciandra, F., Lamba, D., Brancaccio, A., The Structure of the T190M Mutant of Murine α-Dystroglycan at High Resolution:Insight into the Molecular Basis of a Primary Dystroglycanopathy, <<PLOS ONE>>, 2015; 10 (5): N/A-N/A. [doi:10.1371/journal.pone.0124277] [http://hdl.handle.net/10807/72456]
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