Fluorescence polarization and spectropolarimetric studies on the conformational changes induced by ω-aminoacids in two isozymes of glu-plasminogen (I and II)

Abstract

Conformational changes of two isozymes of Glu-plasminogen(Glu-plg I and II) induced by ω-aminoacids were studied by using fluorescence polarization and spectropolarimetry. The rotational relaxation times ( P h ) of FITC labeled Glu-plg I and II decreased in the presence of 6-aminohexanoic acid (6AHA) or tranexamic acid (t-x), which may mean increase in Brownian motion of FITC labeled region (possibly N-terminal region) of Glu-plg I and II when 6AHA or t-x binds with lysine binding sites (LBS) of these plasminogens. Glu-plg II seems to have longer rotational relaxation time compared to that of Glu-plg I, which may mean smaller extent of Brownian motion of FITC labeled region of Glu-plg II in comparison to that of Glu-plg I. The far ultraviolet circular dichroism (CD) spectra indicate that there may be some difference in the polypeptide backbone between Glu-plg I and II, possibly more of β-structure and less of random coil structure in Glu-plg II in comparison to Glu-plg I The presence of 6AHA or t-x gave rise to larger change of the negative ellipticity at around 208 nm in Glu-plg I in comparison to its change in Glu-plg II, which may mean the larger extent of conformational change of Glu-plg I induced by 6AHA or t-x than that of Glu-plg II.