Microenvironment changes in human blood platelet membranes associated with binding of tissue-type plasminogen activator.
Whole washed platelets were labelled with the free radicals [2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinylox y] (16-DOXYL-Ste) or [2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3- oxazolidinyloxy] (5-DOXYL-Ste) and incubated with recombinant tissue-type plasminogen activator (rt-PA). Changes in the membrane fluidity caused by rt-PA were detected by alterations in h+1/h0 calculated from the ESR spectra for 16-DOXYL-Ste and 5-DOXYL-Ste incorporated into the lipid bilayer (h+1 and h0 are the heights of the low-field and middle-field lines of the spectra, respectively). Interaction of rt-PA with both resting and stimulated platelets resulted in increased rigidity of the membrane lipid bilayer as indicated by the reduced value of h+1/h0. This phenomenon can be explained either by conformational changes of membrane receptors caused by the attachment of rt-PA and the subsequent rearrangement of the lipid matrix of platelet membranes, or by the direct association of rt-PA with membrane phospholipids and thus partial embedding of protein molecules into the lipid bilayer restraining lipid mobility.
Department of Biophysics, Medical University of Lodz, Poland.
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Watala
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Pietrucha
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Gwozdzinski
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Kralisz
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Cierniewski
D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism*; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D011994:Recombinant Proteins / Q000378:metabolism; D013113:Spin Labels; D010959:Tissue Plasminogen Activator / Q000378:metabolism*
D003497:Cyclic N-Oxides; D011994:Recombinant Proteins; D013113:Spin Labels; C005072:5-doxylstearic acid; C032363:16-nitroxystearic acid; D010959:Tissue Plasminogen Activator