Cryo-EM structure of the human native plasma coagulation factor XIII complex

Area of Science:

• Biochemistry
• Structural Biology
• Hematology

Background:

• Human coagulation factor XIII (FXIII) is crucial for stabilizing blood clots.
• Previous structural studies focused only on the FXIII-A2 homodimer, leaving the complete FXIII-A2B2 complex structure elusive.
• Understanding FXIII structure is vital for explaining FXIII deficiency.

Purpose of the Study:

• To determine the high-resolution structure of the native human plasma-derived FXIII-A2B2 complex.
• To elucidate the subunit interactions within the FXIII complex.
• To provide structural insights into the molecular basis of FXIII deficiency.

Main Methods:

• Cryogenic electron microscopy (cryo-EM) was used to determine the structure of the FXIII-A2B2 complex.
• Analysis of the high-resolution structure to understand subunit interfaces.
• Investigation of novel mutations in the F13A1 gene from patients with FXIII deficiency.

Main Results:

• The cryo-EM structure of the human FXIII-A2B2 complex was resolved at 2.4 Å resolution.
• A unique "crown"-like assembly was observed, with FXIII-B subunits intercalating with the FXIII-A2 dimer.
• Detailed interactions between FXIII-A and FXIII-B subunits were revealed, including specific Sushi domain interactions.
• The structure elucidated the etiological basis of novel FXIII deficiency mutations, explaining dominant negative effects.

Conclusions:

• The determined FXIII-A2B2 structure provides unprecedented atomic detail of the complex.
• This structural information explains the molecular mechanisms underlying FXIII deficiency.
• The findings bridge structural biochemistry with clinical manifestations of FXIII deficiency.