PROTECTIVE EFFECT OF VITRONECTIN ON OXIDANT-INDUCED INACTIVATION OF RECOMBINANT PLASMINOGEN-ACTIVATOR INHIBITOR TYPE-1 (RPAI-1) - STRUCTURAL AND FUNCTIONAL-ANALYSIS
Sa. Mousa et al., PROTECTIVE EFFECT OF VITRONECTIN ON OXIDANT-INDUCED INACTIVATION OF RECOMBINANT PLASMINOGEN-ACTIVATOR INHIBITOR TYPE-1 (RPAI-1) - STRUCTURAL AND FUNCTIONAL-ANALYSIS, Biochemical archives, 9(3), 1993, pp. 205-216
This study was undertaken to further characterize the nature of the pr
otective effect of vitronectin (VN) on the inhibition of an active for
m of recombinant plasminogen activator inhibitor type 1 (rPAI-1) by va
rious oxidants. The activity of rPAI-1, as determined by its ability t
o neutralize the enzymatic activity of tissue plasminogen activator (t
-PA) in a chromogenic assay, was inhibited by chloramine-T (CT) in con
centration-dependent fashion with an IC50 of 30 uM. This inhibition wa
s antagonized by pretreatment of rPAI-1 with VN (1 to 30 ug/ml) a prot
ective effect that was dependent on the concentration of both the oxid
ant and VN. Interestingly, no other antioxidants including a-tocophero
l, ascorbate, butylated hydroxytoluene, or amino acids such as L-argin
ine or cysteine were able to prevent the inhibition of rPAI-1. To exam
ine the structural basis for the VN effect on rPAI-1, fluorescense spe
ctroscopic studies were performed to determine the effect of CT on the
tryptophan emission intensity (TEI) of rPAI-1. Treatment of rPAI-1 wi
th CT resulted in significant quenching of the TEI of rPAI-1, which is
correlated with the loss of activity of rPAI-1 in neutralizing t-PA.
VN suppressed the quenching effect of CT on the TEI of rPAI-1, indicat
ing that VN may exert its protective effect by maintaining rPAI-1 in a
conformation in which the tryptophans are protected. These results su
ggest a specific mechanism for the protection of rPAI-1 by VN.