Molecular determinants of the reversible membrane anchorage of the G-protein transducin. Export

@article{citeulike:3179939, abstract = {Transducin is a heterotrimer formed by a fatty acylated alpha-subunit and a farnesylated betagamma-subunit. The role of these two covalent modifications and of adjacent hydrophobic and charged amino acid residues in reversible anchoring at disk model membranes is investigated at different pH values, salt concentrations, and lipid packing densities using the monolayer expansion technique and CD spectroscopy. The heterotrimer only binds if the acetylated alpha-subunit is transformed into its surface-active form by divalent cations. In the presence of salts the alpha(GDP)-subunit, the betagamma-complex, and the heterotrimer bind to POPC monolayers at 30 mN/m, estimated to mimic the lateral packing density of disk membranes, with apparent binding constants of Kapp = (1.1 +/- 0.3) x 10(6) M-1 (reflecting the penetration of the fatty acyl chain together with approximately three adjacent hydrophobic amino acid residues), Kapp = (3.5 +/- 0.5) x 10(6) M-1 (reflecting the penetration of the farnesyl chain), and Kapp = (1.6 +/- 0.3) x 10(6) M-1 (reflecting a major contribution of the alpha(GDP)-subunit with only a minor contribution from the betagamma-complex). The apparent binding constant of the alpha(GTP)-subunit is distinctly smaller than that of the alpha(GDP)-subunit. Binding to negatively charged POPC/POPG (75/25 mole/mole) monolayers is reinforced by 2-3 cationic residues for the betagamma-complex. The alpha-subunit shows no electrostatic attraction and the heterotrimer shows even a slight electrostatic repulsion which becomes the dominating force in the absence of salts.}, address = {Institut f\"{u}r Medizinische Physik und Biophysik, Medizinische Fakult\"{a}t Charit\'{e} der Humboldt-Universit\"{a}t, Berlin, Germany.}, author = {Seitz, H. R. and Heck, M. and Hofmann, K. P. and Alt, T. and Pellaud, J. and Seelig, A.}, citeulike-article-id = {3179939}, citeulike-linkout-0 = {http://dx.doi.org/10.1021/bi990298+}, citeulike-linkout-1 = {http://pubs.acs.org/doi/abs/10.1021/bi990298+}, citeulike-linkout-2 = {http://view.ncbi.nlm.nih.gov/pubmed/10387038}, citeulike-linkout-3 = {http://www.hubmed.org/display.cgi?uids=10387038}, day = {22}, doi = {10.1021/bi990298+}, issn = {0006-2960}, journal = {Biochemistry}, keywords = {arf, hetrotrimeric, hetrotrimeric-g-protein, modification, nt}, month = {June}, number = {25}, pages = {7950--7960}, posted-at = {2008-09-01 22:07:05}, priority = {2}, title = {Molecular determinants of the reversible membrane anchorage of the G-protein transducin.}, url = {http://dx.doi.org/10.1021/bi990298+}, volume = {38}, year = {1999} }

TY - JOUR ID - citeulike:3179939 L3 - citeulike-article-id:3179939 N2 - Transducin is a heterotrimer formed by a fatty acylated alpha-subunit and a farnesylated betagamma-subunit. The role of these two covalent modifications and of adjacent hydrophobic and charged amino acid residues in reversible anchoring at disk model membranes is investigated at different pH values, salt concentrations, and lipid packing densities using the monolayer expansion technique and CD spectroscopy. The heterotrimer only binds if the acetylated alpha-subunit is transformed into its surface-active form by divalent cations. In the presence of salts the alpha(GDP)-subunit, the betagamma-complex, and the heterotrimer bind to POPC monolayers at 30 mN/m, estimated to mimic the lateral packing density of disk membranes, with apparent binding constants of Kapp = (1.1 +/- 0.3) x 10(6) M-1 (reflecting the penetration of the fatty acyl chain together with approximately three adjacent hydrophobic amino acid residues), Kapp = (3.5 +/- 0.5) x 10(6) M-1 (reflecting the penetration of the farnesyl chain), and Kapp = (1.6 +/- 0.3) x 10(6) M-1 (reflecting a major contribution of the alpha(GDP)-subunit with only a minor contribution from the betagamma-complex). The apparent binding constant of the alpha(GTP)-subunit is distinctly smaller than that of the alpha(GDP)-subunit. Binding to negatively charged POPC/POPG (75/25 mole/mole) monolayers is reinforced by 2-3 cationic residues for the betagamma-complex. The alpha-subunit shows no electrostatic attraction and the heterotrimer shows even a slight electrostatic repulsion which becomes the dominating force in the absence of salts. IS - 25 JF - Biochemistry SN - 0006-2960 AD - Institut für Medizinische Physik und Biophysik, Medizinische Fakultät Charité der Humboldt-Universität, Berlin, Germany. EP - 7960 TI - Molecular determinants of the reversible membrane anchorage of the G-protein transducin. VL - 38 SP - 7950 KW - arf KW - hetrotrimeric KW - hetrotrimeric-g-protein KW - modification KW - nt AU - Seitz, HR AU - Heck, M AU - Hofmann, KP AU - Alt, T AU - Pellaud, J AU - Seelig, A PY - 1999/06/22/ UR - http://dx.doi.org/10.1021/bi990298+ ER -