Guanidinium and related compounds have been discovered to cause blockade of gramicidin channels in lipid bilayers. The mechanism of binding and blocking by these molecules will be studied using electrophysiological, spectrosopic, and theoretical techniques. Membrane thickness will be varied to evaluate the geometry of the lipid membrane near the channel entrance. Competition between ions and blocking molecules for the gramicidin channel ion-binding site will be examined to evaluate the binding selectivity of the site. Low-conductance variant channels (minis) formed by gramicidin have blocking characteristics which differ from those of typical gramicidin channels, which will be examined in an effort to determine the cause of decreased conductance in minis. analogues of gramicidin with larger pore diameters will be incorporated into bilayers and the blocking characteristics measured in order to test theories about the blocker's binding site. Acyl guanidinium compounds block sodium channels in nerve and acetyl choline channels in neuromuscular junction with a higher potency than guanidinium. The lipid bilayer - gramicidin system will be used to measure the potency of acyl guanidinium compounds as channel blockers. Because in this system the structure of the lipid and protein are well known, this study will allow a detailed examination of the determinants of blocker potency. The results will be compared to the blocks induced by quanidine-like compounds in the channels from oocytes and other tissues. Such information will contribute to the understanding of excitable membrane function and the design of drugs which can serve as specific channel blockers.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM033361-07
Application #
3282995
Study Section
Physiology Study Section (PHY)
Project Start
1983-08-01
Project End
1991-07-31
Budget Start
1989-08-01
Budget End
1990-07-31
Support Year
7
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Brown University
Department
Type
Schools of Medicine
DUNS #
001785542
City
Providence
State
RI
Country
United States
Zip Code
02912
Busath, D D (1993) The use of physical methods in determining gramicidin channel structure and function. Annu Rev Physiol 55:473-501
Seoh, S A; Busath, D (1993) The permeation properties of small organic cations in gramicidin A channels. Biophys J 64:1017-28
Bridal, T R; Busath, D (1992) Inhibition of gramicidin channel activity by local anesthetics. Biochim Biophys Acta 1107:31-8
Turano, B; Pear, M; Busath, D (1992) Gramicidin channel selectivity. Molecular mechanics calculations for formamidinium, guanidinium, and acetamidinium. Biophys J 63:152-61
Bogusz, S; Boxer, A; Busath, D D (1992) An SS1-SS2 beta-barrel structure for the voltage-activated potassium channel. Protein Eng 5:285-93
Hemsley, G; Busath, D (1991) Small iminium ions block gramicidin channels in lipid bilayers. Biophys J 59:901-7
Roeske, R W; Hrinyo-Pavlina, T P; Pottorf, R S et al. (1989) Synthesis and channel properties of [Tau 16]gramicidin A. Biochim Biophys Acta 982:223-7
Busath, D; Szabo, G (1988) Low conductance gramicidin A channels are head-to-head dimers of beta 6.3-helices. Biophys J 53:689-95
Busath, D; Szabo, G (1988) Permeation characteristics of gramicidin conformers. Biophys J 53:697-707
Busath, D D; Hayon, E (1988) Ultraviolet flash photolysis of gramicidin-doped lipid bilayers. Biochim Biophys Acta 944:73-8

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