BIOCHEMISTRY, cilt.54, ss.6123-6131, 2015 (SCI İndekslerine Giren Dergi)
A recently developed membrane-mimetic model was applied to study membrane interaction and binding of the two anchoring C2-like discoidin domains of human coagulation factor Villa (FVIIIa), the Cl and C2 domains. Both individual domains, FVIII Cl and FVIII C2, were observed to bind the phospholipid membrane by partial or full insertion of their extruding loops (the spikes). However, the two domains adopted different molecular orientations in their membrane-bound states; FVIII C2 roughly was positioned normal to the membrane plane, while FVIII Cl displayed a multitude of tilted orientations. The results indicate that FVIII Cl may be important in modulating the orientation of the FVIIIa molecule to optimize the interaction with FIXa, which is anchored to the membrane via its gamma-carboxyglutamic acid-rich (Gla) domain. Additionally, a structural change was observed in FVIII Cl in the coiled main chain leading the first spike. A tight interaction with one lipid per domain, similar to what has been suggested for the homologous FVa C2, is characterized. Finally, we rationalize known FVIII antibody epitopes and the scarcity of documented hemophilic missense mutations related to improper membrane binding of FVIIIa, based on the prevalent nonspecificity of ionic interactions in the simulated membrane-bound states of FVIII Cl and FVIII C2.