title: Factor IX Denver, ASN 346-->ASP mutation resulting in a dysfunctional protein with defective factor VIIIa interaction.
abstract: Hemophilia B is a sex-linked recessive bleeding disorder characterized by the presence of either a decreased amount of normal factor IX (FIX) or the presence of a dysfunctional FIX. We have identified a unique mutation in a family with mild hemophilia B. DNA analysis of family members revealed a single base transition in the 8th exon of the FIX gene predicting an amino acid change of Asn 346-->Asp in the catalytic domain. The FIX variant, named FIX Denver, was purified from proband plasma. Kinetic studies of factor X (FX) interactions with normal FIXa or FIXa Denver and phospholipid (PL) showed little difference in kcat but a significant difference when factor VIIIa (FVIIIa) was included in the reaction. Using kinetic assays to infer the Kd of FIXa for FVIIIa, normal FIXa had a Kd of 0.095 nM while that of FIXa Denver was 9.85 nM. The major defect caused by this point mutation is a marked decrease in the affinity of FIXa Denver for factor VIIIa.
authors.affiliation: Department of Pathology, University of Colorado School of Medicine, Denver 80262, USA. Jerry.Lefkowitz@UCHSC.edu
authors.forename: J B
authors.initials: JB
authors.lastname: Lefkowitz
authors.forename: R
authors.initials: R
authors.lastname: Nuss
authors.forename: T
authors.initials: T
authors.lastname: Haver
authors.forename: L
authors.initials: L
authors.lastname: Jacobson
authors.forename: A R
authors.initials: AR
authors.lastname: Thompson
authors.forename: M
authors.initials: M
authors.lastname: Manco-Johnson
mesh_terms: D000328:Adult; D019943:Amino Acid Substitution; D001780:Blood Coagulation Tests; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004252:DNA Mutational Analysis; D005164:Factor IX / Q000235:genetics* / Q000302:isolation & purification; D015944:Factor VIIIa / Q000378:metabolism; D005170:Factor X / Q000378:metabolism; D002836:Hemophilia B / Q000235:genetics*; D006470:Hemorrhage / Q000209:etiology; D006801:Humans; D007700:Kinetics; D008081:Liposomes / Q000494:pharmacology; D008297:Male; D020125:Mutation, Missense; D009363:Neoplasm Proteins; D010713:Phosphatidylcholines / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D017354:Point Mutation; D013925:Thromboplastin / Q000378:metabolism
chemical_list: D008081:Liposomes; D009363:Neoplasm Proteins; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; C451330:factor IX Denver; D015944:Factor VIIIa; D005164:Factor IX; D005170:Factor X; D013925:Thromboplastin; D003546:Cysteine Endopeptidases; C030910:cancer procoagulant