The Inner Quaternary Ammonium Ion Receptor in Potassium Channels of the Node of Ranvier

نویسندگان

  • Clay M. Armstrong
  • Bertil Hille
چکیده

Quaternary ammonium ions were applied to the inside of single myelinated nerve fibers by diffusion from a cut end. The resulting block of potassium channels in the node of Ranvier was studied under voltage-clamp conditions. The results agree in almost all respects with similar studies by Armstrong of squid giant axons. With tetraethylammonium ion (TEA), pentyltriethylammonium ion (C(5)), or nonyltriethylammonium ion (C(9)) inside the node, potassium current during a depolarization begins to rise at the normal rate, reaches a peak, and then falls again. This unusual inactivation is more complete with C(9) than with TEA. Larger depolarizations give more block. Thus the block of potassium channels grows with time and voltage during a depolarization. The block reverses with repolarization, but for C(9) full reversal takes seconds at -75 mv. The reversal is faster in 120 mM KCl Ringer's and slower during a hyperpolarization to -125 mv. All of these effects contrast with the time and voltage-independent block of potassium, channels seen with external quaternary ammonium ions on the node of Ranvier. External TEA, C(5), and C(9) block without inactivation. The external quaternary ammonium ion receptor appears to be distinct from the inner one. Apparently the inner quaternary ammonium ion receptor can be reached only when the activation gate for potassium channels is open. We suggest that the inner receptor lies within the channel and that the channel is a pore with its activation gate near the axoplasmic end.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Structures of KcsA in Complex with Symmetrical Quaternary Ammonium Compounds Reveal a Hydrophobic Binding Site

Potassium channels allow for the passive movement of potassium ions across the cell membrane and are instrumental in controlling the membrane potential in all cell types. Quaternary ammonium (QA) compounds block potassium channels and have long been used to study the functional and structural properties of these channels. Here we describe the interaction between three symmetrical hydrophobic QA...

متن کامل

Unique Inner Pore Properties of BK Channels Revealed by Quaternary Ammonium Block

Potassium channels have a very wide distribution of single-channel conductance, with BK type Ca(2+)-activated K(+) channels having by far the largest. Even though crystallographic views of K(+) channel pores have become available, the structural basis underlying BK channels' large conductance has not been completely understood. In this study we use intracellularly applied quaternary ammonium co...

متن کامل

Effects of strychnine on the sodium conductance of the frog node of Ranvier

Strychnine blocks sodium conductance in the frog node of Ranvier. This block was studied by reducing and slowing sodium inactivation with scorpion venom. The block is voltage and time dependent. The more positive the axoplasm the greater the block and the faster the approach to equilibrium. Some evidence is presented suggesting that only open channels can be blocked. The block is reduced by rai...

متن کامل

Use-dependent blockers and exit rate of the last ion from the multi-ion pore of a K+ channel.

Quaternary ammonium blockers inhibit many voltage-activated potassium (K+) channels from the intracellular side. When applied to Drosophila Shaker potassium channels expressed in mammalian cells, these rapidly reversible blockers produced use-dependent inhibition through an unusual mechanism--they promoted an intrinsic conformational change known as C-type inactivation, from which recovery is s...

متن کامل

Interaction of Tetraethylammonium Ion Derivatives with the Potassium Channels of Giant Axons

A number of compounds related to TEA(+) (tetraethylammoniumion) were injected into squid axons and their effects on g(K) (the potassium conductance) were determined. In most of these ions a quaternary nitrogen is surrounded by three ethyl groups and a fourth group that is very hydrophobic. Several of the ions cause inactivation of g(K), a type of ionic gating that is not normally seen in squid ...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • The Journal of General Physiology

دوره 59  شماره 

صفحات  -

تاریخ انتشار 1972