Related Experiment Videos
Gramicidins A, B, and C form structurally equivalent ion channels.
D B Sawyer1, L P Williams, W L Whaley
1Department of Physiology and Biophysics, Cornell University Medical College, New York, New York 10021.
Biophysical Journal
|November 1, 1990
Summary
Gramicidins A, B, and C form similar membrane channels, with differences attributed to amino acid substitutions. Hybrid channel analysis confirms structural equivalence in gramicidin membrane channels.
Area of Science:
- Biophysics
- Membrane Protein Structure
- Spectroscopy
Background:
- Gramicidins A, B, and C are naturally occurring peptides known to form membrane channels.
- Previous studies indicated differing properties, particularly for gramicidin B in specific lipid environments, leading to uncertainty about its channel structure.
Purpose of the Study:
- To investigate and clarify the membrane channel structure of gramicidins A, B, and C.
- To determine if structural differences exist between channels formed by these gramicidin variants.
Main Methods:
- Circular dichroism (CD) spectroscopy was employed to analyze peptide structure in different lipid environments.
- Single-channel recording techniques were used to study the functional properties of gramicidin channels in planar bilayers.
Main Results:
- Gramicidins A and B exhibited similar CD spectra when incorporated into dipalmitoylphosphatidylcholine vesicles, suggesting comparable structures.
- Gramicidins A, B, and C formed hybrid channels in planar bilayers with properties intermediate to symmetric channels.
- The formation rates of hybrid channels supported the hypothesis of structurally equivalent gramicidin channels.
Conclusions:
- The structural behavior of gramicidin A, B, and C channels in lipid bilayers is largely equivalent.
- Observed differences in gramicidin channel properties can be explained by amino acid substitutions, specifically at position 11.