title: Hyperinsulinism-Causing Mutations Cause Multiple Molecular Defects in SUR1 NBD1.
abstract: The sulfonylurea receptor 1 (SUR1) protein forms the regulatory subunit in ATP sensitive K+(KATP) channels in the pancreas. SUR proteins are members of the ATP binding cassette (ABC) superfamily of proteins. Binding and hydrolysis of MgATP at the SUR nucleotide binding domains (NBDs) lead to channel opening. Pancreatic KATPchannels play an important role in insulin secretion. SUR1 mutations that result in increased levels of channel opening ultimately inhibit insulin secretion and lead to neonatal diabetes. In contrast, SUR1 mutations that disrupt trafficking and/or decrease gating of KATPchannels cause congenital hyperinsulinism, where oversecretion of insulin occurs even in the presence of low glucose levels. Here, we present data on the effects of specific congenital hyperinsulinism-causing mutations (G716V, R842G, and K890T) located in different regions of the first nucleotide binding domain (NBD1). Nuclear magnetic resonance (NMR) and fluorescence data indicate that the K890T mutation affects residues throughout NBD1, including residues that bind MgATP, NBD2, and coupling helices. The mutations also decrease the MgATP binding affinity of NBD1. Size exclusion and NMR data indicate that the G716V and R842G mutations cause aggregation of NBD1 in vitro, possibly because of destabilization of the domain. These data describe structural characterization of SUR1 NBD1 and shed light on the underlying molecular basis of mutations that cause congenital hyperinsulinism.
authors.affiliation: Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.|Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
authors.forename: Claudia P
authors.initials: CP
authors.lastname: Alvarez
authors.affiliation: Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.|Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.|Department of Cell and Systems Biology, University of Toronto , 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5.
authors.forename: Marijana
authors.initials: M
authors.lastname: Stagljar
authors.affiliation: Department of Molecular Genetics, University of Toronto , 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8.
authors.forename: D Ranjith
authors.initials: DR
authors.lastname: Muhandiram
authors.affiliation: Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.|Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.|Department of Cell and Systems Biology, University of Toronto , 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5.
authors.forename: Voula
authors.identifier: 0000-0001-9262-9954
authors.initials: V
authors.lastname: Kanelis
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000378:metabolism; D019943:Amino Acid Substitution; D001665:Binding Sites; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D006946:Hyperinsulinism / Q000151:congenital / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008239:Lysine / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D010179:Pancreas / Q000378:metabolism / Q000473:pathology; D066329:Protein Aggregates; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D054730:Protein Interaction Domains and Motifs; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D064233:Sulfonylurea Receptors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013912:Threonine / Q000737:chemistry* / Q000378:metabolism
chemical_list: C577507:ABCC8 protein, human; D066329:Protein Aggregates; D011994:Recombinant Proteins; D064233:Sulfonylurea Receptors; D013912:Threonine; D000255:Adenosine Triphosphate; D008239:Lysine