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246 results on '"Gradmann D"'

32. Third symposium onAcetabularia

Author

Alexeev, A. B., Stvolinsky, S. L., Tikhomirova, L. A., Yazykov, A. A., Zubarev, T. N., Apel, K., Bachmann, Peter, Zetsche, Klaus, Bannwarth, Horst, Berger, Sigrid, Boege, Ulrike, Boege, Frank, Gradmann, D., Bokeloh, G., Bonotto, S., Lurquin, P., Baeyens, W., Charles, P., Hoursiangou-Neubrun, D., Mazza, A., Tramontano, G., Felluga, B., BrÄndle, Ernst P. O., Kötter, Renate, Dazy, A. C., Borghi, H., Gauchery, J., Puiseux-Dao, S., Dubacq, J. P., Franke, W. W., Berger, S., Scheer, U., Trendelenburg, M. F., GlÄsel, Rainer M., Herth, Werner, Guillo, M., Karakashian, Marlene W., Kloppstech, Klaus, Koop, Hans-Ulrich, Legros, F., Dumon, I., Hanson, B., Jeanmart, J., Conard, V., Novak, B., Pai, H. S., Dehm, D., Schweiger, M., Rahmsdorf, H. J., Ponta, H., Hirsch-Kauffmann, M., Schweiger, H. G., Schweiger, Hans-Georg, Kretschmer, Horst, Spring, H., Falk, H., Vanden Driessche, T., Delegher-Langohr, V., Hayet, Michèle, Moens, W., Kram, R., Woodcock, C. L. F., Zetsche, K., and Wutz, M.

Published
1975
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37. Electrokinetics of smallest K+ channel: Open state V-sensitivity and inhibition by K+ driving force

Author

Gazzarrini S., Abenavoli A., Gradmann D., Thiel G., and Moroni A.

Abstract

Kcv, isolated from a Chlorella virus, is the smallest known K+ channel. When Kcv is expressed in Xenopus oocytes and exposed to 50 mM: [K+](o), its open-state current-voltage relationship (I-V) has the shape of a "tilted S" between -200 and +120 mV. Details of this shape depend on the conditioning voltage (V (c)) immediately before an I-V recording. Unexpectedly, the I-V relationships, recorded in different [K+](o), do intersect. These characteristics are numerically described here by fits of a kinetic model to the experimental data. In this model, the V (c) sensitivity of I-V is mainly assigned to an affinity increase of external K+ association at more positive voltages. The general, tilted-S shape as well as the unexpected intersections of the I-V relationships are kinetically described by a decrease of the cord conductance by the electrochemical driving force for K+ in either direction, like in fast V-dependent blocking by competing ions.

Published
2007

40. Mutation in pore domain uncovers cation- and voltage-sensitive recovery from inactivation in KAT1 channel

Author

Moroni, A, Gazzarrini, S, Cerana, R, Colombo, R, Sutter, J, Difrancesco, D, Gradmann, D, Thiel, G, Sutter, JU, DiFrancesco, D, Moroni, A, Gazzarrini, S, Cerana, R, Colombo, R, Sutter, J, Difrancesco, D, Gradmann, D, Thiel, G, Sutter, JU, and DiFrancesco, D

Abstract

Effects of threonine substitution by glutamine at position 256 in the pore of the KAT1 channel have been investigated by voltage-clamp, using heterologous gene expression in Xenopus oocytes. The major discrepancy in T256Q from the wild-type channel (wt) was cation specific. While K+ currents were reduced in a largely scalar fashion, the NH4+ current exhibited slow, voltage-dependent inhibition during hyperpolarization. The same effects could be induced in wt, or intensified in T256Q, by addition of the impermeant cation methylammonium (MA+) to the bath. This stresses that both the mutation and MA+ affect a mechanism already present in the wt. Assuming that current inhibition could be described as entry of the channel into an inactive state, we modeled in both wt and in T256Q the relaxation kinetics of the clamp currents by a C-O-I gating scheme, where C (closed) and I (inactivated) are nonconductive states, and O is an open state allowing K+ and NH4+ passage. The key reaction is the transition I-O. This cation- sensitive transition step ensures release of the channel from the inactive state and is ~30 times smaller in T256Q compared to wt. It can be inhibited by external MA+ and is stimulated strongly by K+ and weakly by NH4+. This sensitivity of gating to external cations may prevent K+ leakage from cation-starved cells

Published
2000

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