A hinge region mutation in C1-inhibitor (Ala436-->Thr) results in nonsubstrate-like behavior and in polymerization of the molecule.
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.
Aulak
K S
KS
Division of Nephrology, Children's Hospital Research Foundation, University of Cincinnati College of Medicine, Ohio 45229-2899.
Eldering
E
E
Hack
C E
CE
Lubbers
Y P
YP
Harrison
R A
RA
Mast
A
A
Cicardi
M
M
Davis
A E
AE
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
D003174:Complement C1 Inactivator Proteins; D013912:Threonine; D000409:Alanine