title: Thermodynamic stability, unfolding kinetics, and aggregation of the N-terminal actin-binding domains of utrophin and dystrophin.
abstract: Muscular dystrophy (MD) is the most common genetic lethal disorder in children. Mutations in dystrophin trigger the most common form of MD, Duchenne, and its allelic variant Becker MD. Utrophin is the closest homologue and has been shown to compensate for the loss of dystrophin in human disease animal models. However, the structural and functional similarities and differences between utrophin and dystrophin are less understood. Both proteins interact with actin through their N-terminal actin-binding domain (N-ABD). In this study, we examined the thermodynamic stability and aggregation of utrophin N-ABD and compared with that of dystrophin. Our results show that utrophin N-ABD has spectroscopic properties similar to dystrophin N-ABD. However, utrophin N-ABD has decreased denaturant and thermal stability, unfolds faster, and is correspondingly more susceptible to proteolysis, which might account for its decreased in vivo half-life compared to dystrophin. In addition, utrophin N-ABD aggregates to a lesser extent compared with dystrophin N-ABD, contrary to the general behavior of proteins in which decreased stability enhances protein aggregation. Despite these differences in stability and aggregation, both proteins exhibit deleterious effects of mutations. When utrophin N-ABD mutations analogous in position to the dystrophin disease-causing mutations were generated, they behaved similarly to dystrophin mutants in terms of decreased stability and the formation of cross-β aggregates, indicating a possible role for utrophin mutations in disease mechanisms.
authors.affiliation: Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA.
authors.forename: Surinder M
authors.initials: SM
authors.lastname: Singh
authors.forename: Justine F
authors.initials: JF
authors.lastname: Molas
authors.forename: Narsimulu
authors.initials: N
authors.lastname: Kongari
authors.forename: Swati
authors.initials: S
authors.lastname: Bandi
authors.forename: Geoffrey S
authors.initials: GS
authors.lastname: Armstrong
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Winder
authors.forename: Krishna M G
authors.initials: KM
authors.lastname: Mallela
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002135:Calcium-Binding Proteins / Q000737:chemistry; D002942:Circular Dichroism; D016189:Dystrophin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D055550:Protein Stability; D058767:Protein Unfolding; D016415:Sequence Alignment; D013696:Temperature; D013816:Thermodynamics; D049411:Utrophin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000096985:Calponins
chemical_list: D002135:Calcium-Binding Proteins; D016189:Dystrophin; D008840:Microfilament Proteins; D049411:Utrophin; D000096985:Calponins