Lipid peroxidation decreases the rotational mobility of XXXX in @entity35 liver microsomes.

@entity1447 @entity8798 @entity2003 @entity17690 @entity1110 @entity72906 @entity1234 @entity109 @entity3955 @entity2975 @entity35 @entity10045 @entity214
@entity109 -induced @entity35 liver microsomes were subjected to @entity1110 - and @entity8798 -catalyzed lipid peroxidation. The formation of approx. 95 nmol @entity1234 /mg protein during 18 min peroxidation at 37 degrees C was observed. @entity2003 measured by means of the steady-state fluorescence anisotropy rs of @entity3955 increased in parallel with the @entity1234 formation. Both the amount of @entity1234 and rs remained constant thereafter during incubation of the peroxidized membranes for 2 h. The @entity17690 demethylase activity decreased by about 60% upon lipid peroxidation for 18 min, whereas no significant loss of @entity10045 demethylase activity within the same time range was observed. A time-dependent formation of protein complexes of high molecular weight, comprising most of the microsomal polypeptides, upon lipid peroxidation was observed in @entity214 - @entity2975 gel electrophoresis. The effect of microsomal lipid peroxidation on protein-protein interactions was examined by measuring the rotational mobility of intact @entity1447 . Rotational diffusion was measured by observing the decay of flash-induced absorption anisotropy r(t) of the P-450 X CO complex. Analysis was based on a 'rotation-about-membrane normal' model with the equation r(t) = r1exp(-t/ @entity72906 ) + r2exp(-t/phi 2). In control microsomes, two classes (rapid and slow) of rotating populations of @entity1447 were observed with @entity72906 approximately equal to 150 microseconds, fraction r1/(r1 + r2) approximately equal to 40% and phi 2 approximately equal to 2 ms, fraction r2/(r1 + r2) approximately equal to 60%. A relatively small decrease in the rotational mobility of P-450 was observed by a 18-min lipid peroxidation, while a subsequent incubation of peroxidized microsomes for 2 h at 37 degrees C resulted in a dramatic immobilization of P-450 by the increase of both r2/(r1 + r2) approximately equal to 75% and phi 2 approximately equal to 10-25 ms. The decrease in the P-450 mobility during 18-min lipid peroxidation would be due to the rigidification of the lipid bilayer. However, because the lipid fluidity remained unchanged thereafter, the significant immobilization of P-450 by the subsequent 2-h incubation is deduced to be due to formation of protein aggregates.
