N. Bihoreau et al., COPPER-ATOM IDENTIFICATION IN THE ACTIVE AND INACTIVE FORMS OF PLASMA-DERIVED FVIII AND RECOMBINANT FVIII-DELTA-II, European journal of biochemistry, 222(1), 1994, pp. 41-48
The plasma-derived factor VIII (pd-FVIII) circulates as different hete
rodimers of heavy and light chains associated by a metallic ion still
present in the functional activated factor Vm trimer of molecular mass
50000-45000-70000 Da. The chelation of the metal leads to the dissoci
ation of these complexes with a concomitant loss of the procoagulant a
ctivity. Until now, this ion has not been directly identified and its
role in the structure/function relationships remains unclear. We repor
t the first determination of the nature of this metal using atomic-abs
orption spectroscopy with Zeeman effect. A comparative identification
was also performed with the new recombinant factor VIII, FVIII-Delta I
I. In the different active pd-FVIII heterodimers (of molecular mass ra
nging over 210000-80000-90000-80000 Da) and in FVIII-Delta II, copper
was detected. This result is consistent with sequence similarities des
cribed between FVIII and copper-binding proteins. The quantification o
f the copper content in FVIII-Delta II and in the corresponding pd-FVI
II dimer of 90000-80000 Da indicated, for both proteins, the presence
of one copper ion/mol FVIII. Copper was also identified in the activat
ed FVIII complex and remained in the dimer of 50000-70000 Da generated
during FVIII inactivation. Further dissociation into isolated fragmen
ts of molecular masses 70000 Da and 50000 Da was concomitant with the
loss of the copper ion. No copper was detected in the isolated fragmen
t of molecular mass 45000 Da. These results suggest that the presence
of the cation is not directly related to FVIII activity but is an esse
ntial structural prerequisite for FVIII heavy-light-chain association.