Factor XIII: novel structural and functional aspects

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Factor XIII (FXIII) is a protransglutaminase essential for hemostasis and possesses diverse intracellular functions.
• Plasmatic FXIII (pFXIII) is a tetramer (FXIII-A2B2), while cellular FXIII (cFXIII) is a dimer (FXIII-A2).
• FXIII-A shares conserved structural domains with other transglutaminases, while FXIII-B is a glycoprotein composed of sushi domains.

Purpose of the Study:

• To elucidate the structural elements of FXIII-A involved in FXIII-B interaction.
• To review the activation process of pFXIII and cFXIII.
• To present a molecular model of FXIIIa structure and discuss its implications for enzyme activity.

Main Methods:

• Literature review and analysis of structural and biochemical studies.
• Molecular modeling based on analogies with transglutaminase-2.
• Biochemical studies to validate structural models.

Main Results:

• The first sushi domain of FXIII-B appears critical for complex formation with FXIII-A.
• pFXIII activation involves thrombin cleavage, Ca(2+) -dependent dissociation of FXIII-B, and fibrinogen acceleration.
• cFXIII activation bypasses proteolysis.
• A molecular model of FXIIIa structure was developed, aligning with biochemical findings.

Conclusions:

• Understanding FXIII structure-function relationships is vital for its roles in hemostasis and cellular processes.
• The molecular model provides insights into FXIIIa's active conformation and substrate interactions.
• Further research into FXIII's structural dynamics can illuminate its therapeutic potential.