INVESTIGADORES
CARRIZO GARCIA Maria elena
congresos y reuniones científicas
Título:
Glycogen storage disease-associated glycogenin Ala16Pro mutation reduces the enzyme substrate binding affinity through a conformational change
Autor/es:
MUÑOZ SOSA, CHRISTIAN J.; CURTINO, JUAN A.; CARRIZO, MARÍA E.
Lugar:
Rio de Janeiro
Reunión:
Congreso; 5th Latin American Protein Society Meeting (LAPSM); 2016
Institución organizadora:
Latin American Protein Society
Resumen:
Glycogen storage diseases (GSD) are inherited metabolic disorders involving the enzymes responsible for the synthesis and degradation of glycogen. They are characterized by accumulation of the polysaccharide with abnormal chemical structure or in an abnormal amount. GSD type 15 is an extremely rare genetic disorder reported only in a few patients to date. It is caused by mutations in the GYG1 gene, which encodes glycogenin-1, one of the isoforms of human glycogenin. This enzyme initiates glycogen biosynthesis by autoglucosylation from UDP-glucose and Mn2+, producing the oligosaccharide substrate of glycogen synthase. One of the most recently described cases of GSD type 15 (1) corresponds to a patient that was homozygous for an N-terminal missense variant (c.46G>C, p.Ala16Pro). The patient exhibited skeletal myopathy with storage of polyglucosan in muscle fibers and no cardiac involvement.Ala16 is conserved in many members of glycogenin family, thus it was of interest to analyze the effect of its substitution on the catalytic properties of the protein in order to understand its role in the pathology. Since human and rabbit glycogenin amino acid sequences are 93% identical, we have introduced Ala16Pro mutation into rabbit enzyme and expressed the mutant in E. coli. In this work, we present the analysis of the effect of the mutation on the autoglucosylation, transglucosylation and UDP-glucose hydrolytic activities of the protein as well as on its substrate binding affinity. Our results suggests that even though Ala16 is not directly involved in UDP-glucose binding, its replacement by Pro would promote a conformational change that would cause a reduction in the substrate binding affinity and, consequently, the loss of enzyme activity.1. Malfatti, E., et al. (2014) Annals of neurology 76, 891-898.