The ionization state and the conformation of Glu-71 in the KcsA K(+) channel

Bernèche, Simon and Roux, Benoît. (2002) The ionization state and the conformation of Glu-71 in the KcsA K(+) channel. Biophysical journal, Vol. 82, H. 2. pp. 772-780.

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Official URL: http://edoc.unibas.ch/dok/A5249316

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The side chain of Glu-71 of the KcsA K(+) channel, an important residue in the vicinity of the selectivity filter, was not resolved in the crystallographic structure of Doyle et al. (Doyle, D. A., J. M. Cabral, R. A. Pfuetzner, A. Kuo, J. M. Gulbis, S. L. Cohen, B. T. Chait, and R. MacKinnon. 1998. Science. 280:69-77). Its atomic coordinates are undetermined and its ionization state is unknown. For meaningful theoretical and computational studies of the KcsA K(+) channel, it is essential to address questions about the conformation and the ionization state of this residue in detail. In previous MD simulations in which the side chain of Glu-71 is protonated and forming a strong hydrogen bond with Asp-80 it was observed that the channel did not deviate significantly from the crystallographic structure (Bernèche, S., and B. Roux. 2000. Biophys. J. 78:2900-2917). In contrast, we show here that the structure of the selectivity filter of the KcsA channel is significantly disrupted when these side chains are fully ionized on each of the four monomers. To further resolve questions about the ionization state of Glu-71 we calculated the pK(a) value of this residue using molecular dynamics free energy simulations (MD/FES) with a fully flexible system including explicit solvent and membrane and finite-difference Poisson-Boltzmann (PB) continuum electrostatics. It is found that the pK(a) of Glu-71 is shifted by approximately +10 pK(a) units. These results strongly suggest that Glu-71 is protonated under normal conditions.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Computational Biophysics (Bernèche)
UniBasel Contributors:Bernèche, Simon
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Biophysical Society
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:19
Deposited On:22 Mar 2012 13:16

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