Effects of lanthanide ions on the binding ability of annexin V to phospholipid vesicle.
The effects of lanthanide ions (Ln(3+)), La(3+), Ce(3+), Gd(3+), and Tb(3+), on the binding ability of annexin V to phospholipid vesicle were studied, and compared with that of Ca(2+). The energy transfer following excitation at 278 nm was accompanied by a small decrease (about 3%) in the fluorescence signal (310-315 nm) of the aromatic amino acid residues, followed by strong re-emission of annexin V-bound Tb(3+) at 547 nm. The results of the titration of Tb(3+)-protein interactions using the rate dialysis method suggest that there are two high affinity metal binding sites on annexin V, to which Tb(3+) binds with an average dissociation constant, Kd, of about 2.11 x 10(-7) M. The Ln(3+) seemed to assist the anticoagulant action of annexin V because it binds more strongly to phospholipid than Ca(2+) does. Annexin V had the same ability to bind phospholipids in 10 mu M Ln(3+) as it did in 1 InM Ca(2+), showing that it binds to anionic phospholipids with Ln(3+) more strongly than it does with Ca(2+).
Funakoshi
T
T
Department of Hygienic Chemistry, Faculty of Pharmaceutical Science Kumamoto University, Japan.
Furushima
K
K
Mizokami
H
H
Kojima
S
S
D017304:Annexin A5 / Q000378:metabolism*; D006801:Humans; D008674:Metals, Rare Earth / Q000494:pharmacology; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects
D017304:Annexin A5; D008674:Metals, Rare Earth; D010743:Phospholipids