Electrostatic effects on ion selectivity and rectification in designed ion channel peptides

  • Lear J
  • Schneider J
  • Kienker P
 et al. 
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Abstract

To help determine how amino acid sequence can influence ionic conduction
properties in alpha-helical structures, we have synthesized and studied
three closely related, channel-forming peptides. The sequences are
based on a 21-residue amphiphilic Leu-Ser-Ser-Leu-Leu-Ser-Leu heptad
repeat motif and differ in having either neutral, negatively, or
positively charged N-termini. The channels formed by the neutral
peptide are modestly cation selective and exhibit asymmetric current-voltage
curves arising from the partial charges at the ends of the alpha-helix.
Addition of a negatively charged Glu residue converted the channel
to a completely cation-selective structure and essentially eliminated
its rectification. Addition of a positively charged Arg residue near
the N-terminus of the peptide reduced this channel's cation selectivity
and increased the extent of rectification, These effects on channel
ionic conductance can be explained by a theoretical electrostatic
model and provide insights into the workings of more complex channel
proteins.

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Authors

  • J. D. Lear

  • J. P. Schneider

  • P. K. Kienker

  • W. F. DeGrado

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