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Blood Coagul Fibrinolysis. 2003 Jun;14(4):401-5.

A novel type I factor X variant (factor X Cys350Phe) due to loss of a disulfide bond in the catalytic domain.

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Department of Medical and Surgical Sciences, Second Chair of Medicine, via Ospedale 105, University of Padua Medical School, Padua, Italy.


We report a novel mutation within the coagulation factor X (FX) that we have designated FX Padua 4. The phenotype and genotype of the proband and family members were studied. The proband was a child affected by a complex neurological syndrome who, after birth, experienced severe bleeding. The proband showed a laboratory pattern characterized by a severe reduction of FX activity and FX antigen, suggesting a true deficiency. Molecular analysis disclosed a new FX mutation localized in the catalytic domain responsible for a Cys350Phe substitution. The proband was homozygous for this mutation. The proband's mother and father showed a heterozygous pattern and had approximately one-half the normal FX activity and FX antigen. Residual purified FX Cys350Phe had an identical behavior to normal FX as showed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Molecular modeling confirms that the mutation leads to the disruption of a disulfide bridge in the catalytic region of FX. Comparison with other topologically equivalent mutations in other vitamin K-dependent proteins suggests that this disruption could adversely affect protein folding/stability, accounting for the cross-reactive material negative phenotype.

[Indexed for MEDLINE]

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