J. Biol. Chem., Vol. 261, Issue 23, 10598-10605, Aug, 1986
Chemical modification of bovine prothrombin fragment 1 in the presence of Tb3+ ions
SF Wright, P Berkowitz, DW Deerfield 2d, PA Byrd, DL Olson, RS Larson, GC Hinn, KA Koehler, LG Pedersen and RG Hiskey
The formaldehyde-morpholine method for the conversion of gamma-
carboxyglutamyl (Gla) residues to gamma-methyleneglutamyl (gamma-MGlu)
residues has been applied to the modification of bovine prothrombin
fragment 1. In the absence of Tb3+ ions or at Tb3+ ion concentrations of 2
Km app and 25 Km app the action of 10,000-fold molar excess of formaldehyde
and morpholine, pH 5.0, converts the 10 Gla residues of the protein into 10
gamma-MGlu residues. Modification of the protein using the same conditions
but increasing the Tb3+ concentration to 100 Km app provided a homogeneous
protein containing 3 gamma-MGlu and 7 Gla residues, bovine 3
gamma-MGlu-fragment 1. The modified protein binds the same number of Ca2+
ions (6-7) as bovine fragment 1. However, the positive cooperatively
associated with Ca2+ binding is abolished and the overall affinity for Ca2+
ions is reduced. Fluorescence titrations of 3 gamma-MGlu-fragment 1 using
either Ca2+ or Mg2+ ions indicate that the modified protein retains a
fluorescence quenching behavior similar to that of the native protein. The
modified protein does not bind to phosphatidylserine/phosphatidylcholine
vesicles in the presence of Ca2+ ions. Thus the metal ion-induced
fluorescence transition exhibited by the bovine protein appears to be a
necessary but not sufficient condition for phospholipid binding.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?