tailieunhanh - Báo cáo Y học: Fluorescence study of the high pressure-induced denaturation of skeletal muscle actin

Ikkai&Ooi [Ikkai,T.&Ooi,T. (1966)Biochemistry5, 1551± 1560] made a thorough study of the e ect of pressure on G- and F-actins. However, all of the measurements in their study were made after the release of pressure. In the present experiment in situ observations were attempted by using eATP to obtain further detailed kinetic and thermodynamic information about the behaviour of actin under pressure. | Eur. J. Biochem. 269 364-371 2002 FEBS 2002 Fluorescence study of the high pressure-induced denaturation of skeletal muscle actin Yoshihide Ikeuchi1 Atsusi Suzuki2 Takayoshi Oota2 Kazuaki Hagiwara2 Ryuichi Tatsumi1 Tatsumi Ito1 and Claude Balny3 1 Department of Bioscience and Biotechnology Graduate School of Agriculture Kyushu University Fukuoka Japan department of Applied Biological Chemistry Faculty of Agriculture Niigata University Japan 3INSERM Unite 128 IFR 24 CNRS Montpellier France Ikkai Ooi Ikkai T. Ooi T. 1966 Biochemistry 5 15511560 made a thorough study of the effect of pressure on G- and F-actins. However all of the measurements in their study were made after the release of pressure. In the present experiment in situ observations were attempted by using eATP to obtain further detailed kinetic and thermodynamic information about the behaviour of actin under pressure. The dissociation rate constants of nucleotides from actin molecules the decay curve of the intensity of fluorescence of eATP-G-actin or eADP-F-actin followed first-order kinetics. The volume changes for the denaturation of G-actin and F-actin were estimated to be -72 mL-mol-1 and -67 mL-mol-1 in the presence of ATP respectively. Changes in the intensity of fluorescence of F-actin whilst under pressure suggested that eADP F-actin was initially depolymerized to eADP-G-actin subsequently there was quick exchange of the eADP for free eATP and then polymerization occurred again with the liberation of phosphate from eATP bound to G-actin in the presence of excess ATP. In the higher pressure range 250 MPa the partial collapse of the three-dimensional structure of actin which had been depolymerized under pressure proceeded immediately after release of the nucleotide so that it lost the ability to exchange bound ADP with external free ATP and so was denatured irreversibly. An experiment monitoring eATP fluorescence also demonstrated that in the absence of Mg2 -ATP the dissociation of actin-heavy .