Iion transport through the potassium channels of biological membranes

Ait'yan, S. Kh; Kalaxdadze, I.L.; Chizmadjev, Yu.A.

doi:10.1016/0302-4598(77)80003-2

Cited by 11 publications

(7 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The elements of the theory are the same as those in several previous papers (Heckmann, a, b, 1968Hill and Chen, 1971;Hladky, 1972;L/iuger, 1973;Markin and Chizmadjev, 1974;Chizmadjev and Aityan, 1977;Aityan and Kalandadze, 1977;Aityan et al, 1977, Kohler, 1977Levitt, 1978 b). We use some of the notation of .…”

Section: Theorymentioning

confidence: 94%

“…In this example and in later calculations with the three-site model, the repulsion terms are powers of a basic term Fout chosen to satisfy the principle of detailed balances (e.g., Hill, 1977) and the arbitrary assumption of a linear potential drop between wells as follows: for the transitions 00K -K0K and K0K -0KK, Four; for 0K0 -KK0, Fo, t2; and for 0KK -KKK, Fo,t 3. A similar choice of repulsion terms was made by Aityan and Kalandadze (1977). The four curves in Fig.…”

Section: Occupancy and Conductancementioning

confidence: 99%

See 1 more Smart Citation

Potassium channels as multi-ion single-file pores.

Hille¹,

Schwarz²

1978

The Journal of General Physiology

784

715

View full text Add to dashboard Cite

a B S TRAC T A literature review reveals many lines of evidence that both delayed rectifier and inward rectifier potassium channels are multi-ion pores. These include unidirectional flux ratios given by the 2-2.5 power of the electrochemical activity ratio, very steeply voltage-dependent block with monovalent blocking ions, relief of block by permeant ions added to the side opposite from the blocking ion, rectification depending on E -EK, and a minimum in the reversal potential or conductance as external K + ions are replaced by an equivalent concentration of TI + ions. We consider a channel with a linear sequence of energy barriers and binding sites. The channel can be occupied by more than one ion at a time, and ions hop in single file into vacant sites with rate constants that depend on barrier heights, membrane potential, and interionic repulsion. Such multi-ion models reproduce qualitatively the special flux properties of potassium channels when the barriers fi~r hopping out of the pore are larger than for hopping between sites within the pore and when there is repulsion between ions. These conditions also produce multiple maxima in the conductance-ion activity relationship. In agreement with Armstrong's hypothesis (1969.J. Gen. Physiol. 54:553-575), inward rectification may be understood in terms of block by an internal blocking cation. Potassium channels must have at least three sites and often contain at least two ions at a time.Evidence has accumulated, for the sodium channel and for several types of potassium channels of electrically excitable cells, that ions interact with the channel and with other ions in it while diffusing across the membrane (French and Adelman, 1976). An earlier paper of Hille (1975 b) discussed a model of the sodium channel in which the permeating ion must pass across a sequence of four energy barriers to cross the membrane. Inasmuch as the model assumed that no more than one ion could be in the channel at a time, it was called a oneion pore. In this paper we consider a similar type of linear, multibarrier model for a multi-ion pore where more than one ion may be in a channel at a time, and the ions are not permitted to pass by each other as they move through the channel. These assumptions lead to phenomena commonly referred to as "single-file diffusion" or the "long pore effect" which have been reported in measurements of the passive movement of ions in potassium channels of nerve, muscle, and other cell membranes. Our goal is to show that the major transport properties of potassium channels may be accounted for by this class of multi-ion channel models. For practical reasons, only a qualitative agreement is demonstrated here. An attempt to make more realistic models would need many more J. GEN. PHYSIOL. 9 The Rockefeller University Press .

show abstract

Section: Theorymentioning

confidence: 94%

Section: Occupancy and Conductancementioning

confidence: 99%

Potassium channels as multi-ion single-file pores.

Hille¹,

Schwarz²

1978

The Journal of General Physiology

784

715

View full text Add to dashboard Cite

show abstract

“…The aim ofthe present work was to elaborate the original ideas put forward by Lauger and others (Lauger et al, 1980;Ciani, 1984;Lauger, 1985;Mironov, 1988;Lux et al, 1990). New mechanism of channel permeation suggested in the present paper was analyzed for experimental protocols previously assumed to be indicative of multiple occupancy and ion-ion interactions within the channel (Heckmann, 1972;Aityan et al, 1977;Hille and Schwartz, 1978;Urban et al, 1980;Eisenmann and Horn, 1983). The evidence for the channel to be a multiion pore was based on one of the following criteria: (a) the Ussing flux ratio exponent is larger than unity; (b) in the presence of two permeating ions with their constant total concentration, the channel current has an anomalous mole fraction dependence; the conductance-concentration relationship does not correspond to the Michaelis-Menten equation, revealing a maximum (c) or possessing another slope (d); (e) the ion block has an unusually strong voltage dependence.…”

Section: Introduction Theorymentioning

confidence: 99%

Conformational model for ion permeation in membrane channels: a comparison with multi-ion models and applications to calcium channel permeability

Mironov¹

1992

Biophysical Journal

View full text Add to dashboard Cite

The permeation properties of ion channels existing in several conductive states were analyzed. Each state was represented by the one-ion model. A special emphasis was placed on features, assumed to be indicative of a multi-ion mode of channel occupancy such as a deviation of concentration dependence of channel conductance from the Michaelis-Menten equation, an anomalous mole fraction effect, a strong voltage dependence of ion block and coupling of unidirectional fluxes (anomalous Ussing flux ratio). The conformational model was shown to have all these properties. The ion permeation through voltage-sensitive calcium channels fulfilled all the characteristics of the model proposed.

show abstract

“…Much evidence has now accumulated that channels in excitable membranes, such as the potassium channel in squid axon, may accommodate more than one ion at a time [1,12,31,36]. In such multiplyoccupied channels ions may interact with each other.…”

Section: Ion-ion Interaction In Channelsmentioning

confidence: 99%

“…The rate constants determined in this way have to be considered as tentative since the analysis is based on a limited set of steady-state experiments (electrical relaxation studies of ion transfer kinetics in the channel have not been done so far). More complicated models with more than two binding sites have also been applied to the analysis of conductance and biionic potential measurements 1,25,61].…”

Section: The Gramieidin Channel As a Model Channelmentioning

confidence: 99%

Kinetic properties of ion carriers and channels

Läuger

1980

J. Membrain Biol.

205

View full text Add to dashboard Cite

Ions and other hydrophilic substances permeate through cellular membranes by means of special mechanisms different from simple diffusion through the lipid bilayer. In the discussion of possible transport pathways, two alternatives are usually considered: carrier and channel mechanisms. A carrier (in its simplest form) may be defined as a transport system with a binding side that is exposed alternately to the left and to the right side (but not to both sides simultaneously). A channel, on the other hand, consists of one or several binding sites arranged in a transmembrane sequence and is accessible from both sides at the same time.Clear-cut examples of carrier and channel mechanisms in ion transport have been obtained from the study of certain small or medium-sized peptides and depsipeptides produced by microorganisms. Cyclodepsipeptides, such as valinomycin, have been shown to act by a translatory carrier mechanism which involves a movement of the whole carrier molecule with respect to the lipid matrix of the membrane. A well-characterized ion channel is the channel formed by the linear pentadecapeptide, gramicidin A. In these cases the distinction between a channel which is more or less fixed within the membrane and a carrier moving within the lipid matrix is unambiguous. The discrimination between carrier and channel mechanisms becomes less obvious, however, in the case of large membrane proteins spanning the lipid bilayer, which are thought to be responsible for ion transport across the cell membrane. Such a protein is unlikely to move as a whole within the membrane. It still can act as carrier (according to the definition given above), however, ira conformational change within the protein switches the binding site from a left-exposed to a right-exposed state. A channel, on the other hand, does not necessarily have a fixed, time-independent structure. Proteins may assume many conformational substates and move from one state to the other. Accordingly, in a channel conformational transitions may occur between states differing in the height of the energy barriers that restrict the movement of the ion. It can be shown that such a channel with multiple conformational states may approach the kinetic behavior of a carrier. Channel and carrier models should therefore not be regarded as mutually exclusive possibilities, but rather as limiting cases of a more general mechanism.In this article first the kinetic properties of wellstudied examples of carriers and channels will be reviewed, namely, translatory ion carriers of the valinomycin type and ion channels formed by peptides such as gramicidin A. This will be followed by a theoretical treatment of ion movement in channels with fixed structure and a comparison of the transport properties of simple carriers and channels. In the last part of the article, the more general concept of channels with multiple conformational states will be discussed, which allows one to describe carrier and channel mechanisms from a common point of view. The same concept will also be applied ...

show abstract

Iion transport through the potassium channels of biological membranes

Cited by 11 publications

References 7 publications

Potassium channels as multi-ion single-file pores.

Potassium channels as multi-ion single-file pores.

Conformational model for ion permeation in membrane channels: a comparison with multi-ion models and applications to calcium channel permeability

Kinetic properties of ion carriers and channels

Contact Info

Product

Resources

About