Fig. 1: The N-terminal segment of the FVIII B domain interacts with MCFD2/ERGIC-53^CRD.

a Schematic representation of the domains in factors V and VIII. Conserved domains and the range of amino acid residues comprising each domain are indicated. The SDLL(-/M)LL(K/R)QS consensus motifs identified in FV and FVIII are highlighted in red. N-linked glycosylation sites as annotated in the UniProt database (P12259 and P00451), are represented. b ¹H–¹⁵N heteronuclear single quantum coherence (HSQC) spectra of the ¹⁵N-labeled FVIII-derived peptide (Asn776–Asp838) alone (black) or in the presence of one molar equivalent of MCFD2/ERGIC-53^CRD (left) or MCFD2 (right). The ¹⁵N-labeled FVIII-derived peptide (0.1 mM) was dissolved in 20 mM MES (pH 6.0) containing 10 mM CaCl₂, 150 mM NaCl, and 10% (v/v) D₂O. NMR spectra were acquired at 283 K. c Plots of the intensity ratios of the backbone amide peaks of the FVIII-derived peptide with versus without MCFD2/ERGIC-53^CRD (upper) or MCFD2 only (lower). Pink bars indicate residues whose NMR peaks were undetectable due to extreme broadening upon addition of MCFD2/ERGIC-53^CRD. In the profiles of intensity ratio, residues for which the ¹H–¹⁵N HSQC peaks could not be observed because of peak overlapping and/or broadening were denoted with asterisks, whereas proline residues were denoted with “P”.