title: Impaired dimer assembly and decreased stability of naturally recurring R260C mutant A subunit for coagulation factor XIII.
abstract: Factor XIII (FXIII) consists of catalytic A subunits (FXIII-A) and carrier B subunits. Congenital FXIII deficiency is a severe bleeding disorder. We previously identified an R260C missense mutation and an exon-IV deletion in Japanese patients' F13A genes. To characterize the molecular basis of this disease, we expressed a wild-type and the mutant FXIII-A in yeast cells for detailed investigation, by taking advantage of yeast's ability for mass protein production. The mutant proteins were expressed less efficiently than the wild-type and considerably aggregated; even their non-aggregated forms became aggregated with time. Ultra-centrifugation and gel-filtration analyses revealed that the mutants were of extremely high-molecular weight, and that the wild-type formed a dimer. Notably, a part of the R260C mutant was found in monomer form. This was consistent with the prediction by molecular modelling that the mutant molecule would lose the electrostatic interaction between the two monomers, leading to their inability to form a dimer. The mutants lost enzymatic activity. The mutants were only partially converted by thrombin to the cleaved form. The wild-type was fully converted and activated. These mutants might have significantly altered conformations, resulting in their aggregation in vitro, and may ultimately lead to FXIII deficiency in vivo as well.
authors.affiliation: Department of Molecular Patho-Biochemistry and Patho-Biology, Yamagata University School of Medicine, Yamagata, 990-9585 Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Maeda
authors.forename: Wei Guang
authors.initials: WG
authors.lastname: Zhang
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Souri
authors.forename: Vivien C
authors.initials: VC
authors.lastname: Yee
authors.forename: Akitada
authors.initials: A
authors.lastname: Ichinose
mesh_terms: D005176:Factor XIII / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D005177:Factor XIII Deficiency / Q000235:genetics*; D006801:Humans; D008958:Models, Molecular; D020125:Mutation, Missense; D055503:Protein Multimerization / Q000235:genetics*; D055550:Protein Stability; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D011994:Recombinant Proteins; D005176:Factor XIII