title: A hinge region mutation in C1-inhibitor (Ala436-->Thr) results in nonsubstrate-like behavior and in polymerization of the molecule.
abstract: C1-inhibitor(Mo), a dysfunctional C1-inhibitor molecule produced in two kindred with type II hereditary angioedema, has a mutation at the P10 position (Ala436 to Thr). Like most serpins with hinge region mutations (P14, P12, P10), C1-inhibitor(Mo) loses its inhibitory activity. However, unlike the other hinge region mutations, this mutant is not converted to a substrate. As shown by nondenaturing gel electrophoresis, gel filtration, sucrose density gradient ultracentrifugation, and electron microscopy, C1-inhibitor(Mo) exists in both monomeric and multimeric forms. Polymerization probably results from reactive center loop insertion into the A sheet of an adjacent molecule. Native C1-inhibitor(Mo) was shown to have a thermal stability profile intermediate to those of intact and of cleaved normal C1-inhibitor. Native C1-inhibitor(Mo) did not bind to monoclonal antibody KII, which binds only to reactive center-cleaved normal C1-inhibitor. It did, however, react with monoclonal antibody KOK12, which recognizes complexed or cleaved C1-inhibitor but not intact normal C1-inhibitor. Native C1-inhibitor(Mo), therefore, exists in a conformation similar to the complexed form of normal C1-inhibitor.
authors.affiliation: Division of Nephrology, Children's Hospital Research Foundation, University of Cincinnati College of Medicine, Ohio 45229-2899.
authors.forename: K S
authors.initials: KS
authors.lastname: Aulak
authors.forename: E
authors.initials: E
authors.lastname: Eldering
authors.forename: C E
authors.initials: CE
authors.lastname: Hack
authors.forename: Y P
authors.initials: YP
authors.lastname: Lubbers
authors.forename: R A
authors.initials: RA
authors.lastname: Harrison
authors.forename: A
authors.initials: A
authors.lastname: Mast
authors.forename: M
authors.initials: M
authors.lastname: Cicardi
authors.forename: A E
authors.initials: AE
authors.lastname: Davis
mesh_terms: D000409:Alanine; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D003174:Complement C1 Inactivator Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D004355:Drug Stability; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008854:Microscopy, Electron; D017354:Point Mutation; D011489:Protein Denaturation; D013816:Thermodynamics; D013912:Threonine; D014162:Transfection
chemical_list: D003174:Complement C1 Inactivator Proteins; D013912:Threonine; D000409:Alanine