These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Rotation of cytochrome P-450. I. Investigations of protein-protein interactions of cytochrome P-450 in phospholipid vesicles and liver microsomes.
    Author: Kawato S, Gut J, Cherry RJ, Winterhalter KH, Richter C.
    Journal: J Biol Chem; 1982 Jun 25; 257(12):7023-9. PubMed ID: 7085615.
    Abstract:
    Rotation of cytochrome P-450 was examined in both liver microsomes and reconstituted and phospholipid vesicles. Purified cytochrome P-450 was incorporated into lipid vesicles composed of phosphatidylcholine-phosphatidylethanolamine-Phosphatidylserne. Rotational diffusion was measured by detecting the decay of absorption anisotropy, r(t), after photolysis of the heme. CO complex by a vertically polarized laser flash. No contribution of vesicle tumbling to r(t) was observed over the experimental time range of 0-500 mus for samples in 60% sucrose. Analysis of r(t) was based on a "rotation-about-membrane normal" model. The measurements were used to investigate intermolecular interactions of cytochrome P-450. In vesicles of a high lipid to protein ratio (=30 by weight), the residual time-independent normalized anisotropy, r (infinity)/r (0), reached a limiting low value, implying that all cytochrome P-450 was rotating. The mean rotational relaxation time, phi 1, was about 95 mus. In contrast, about 35% of cytochrome P-450 was immobilized in vesicles of a low lipid to protein ratio (=1), with phi 1 of about 95 mus for the mobile fraction. The immobile fraction is presumably due to self-aggregation of cytochrome P-450. In rat liver microsomes, 0-50% of cytochrome P-450 was mobile with phi 1 of about 120 mus at 20 degrees C, and the rest was immobile. A significant temperature dependence of r(t) was observed in microsomes. All cytochrome P-450 was immobile below 7 degrees C, and about 50% of the enzyme was mobile at 37 degrees C with phi 1 approximately 60 mus. From the limiting value of r(infinity)/r(0) congruent to 0.12, the tilt angle of the heme plane of cytochrome p-450 from the membrane plane was calculated to be about 40 degrees.
    [Abstract] [Full Text] [Related] [New Search]