New insights into multiple coagulation factor deficiency from the solution structure of human MCFD2

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Human MCFD2 (multiple coagulation factor deficiency 2) is crucial for transporting coagulation factors V and VIII.
• Mutations in MCFD2 or ERGIC-53 cause combined deficiency of factors V and VIII (F5F8D), a mild inherited hemophilia.
• The precise function of MCFD2 in the secretory pathway remains unclear, despite its known interactions.

Purpose of the Study:

• To elucidate the structure of human MCFD2 in solution using NMR.
• To understand the mechanism underlying F5F8D caused by MCFD2 mutations.
• To clarify the role of calcium ions in MCFD2 structure and function.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to determine the solution structure of human MCFD2.
• NMR studies were conducted on wild-type MCFD2 and two disease-causing mutant variants.
• Calcium ion (Ca(2+)) binding effects on protein folding were investigated.

Main Results:

• MCFD2 structure is dependent on calcium ion availability; it is disordered in the apo state.
• Ca(2+) binding induces folding of MCFD2 via its C-terminal EF-hand motifs, with some N-terminal disorder persisting.
• Disease-associated MCFD2 mutants exhibit significant disorder even in the presence of calcium ions.

Conclusions:

• The findings explain the calcium-dependent interaction between MCFD2 and ERGIC-53.
• The structural disorder of mutant MCFD2 provides a molecular basis for impaired secretion of coagulation factors V and VIII.
• This study clarifies the mechanism by which MCFD2 mutations lead to combined factor V and VIII deficiency.