In about 150 mM K1, the selectivity
filter contains two K1 ions (Figs. 6 and 8).
The ions are located at opposite ends of the
selectivity filter, separated by about 7.5 Å,
roughly the average distance between K1
ions in a 4 M KCl solution, and in the
selectivity filter there are no intervening
Cl2 anions to balance the charge. We
therefore conclude that the selectivity filter
attracts and concentrates K1 ions. But how
does such a selectivity filter ever conduct
ions? The structure implies that a single K1
ion would be held very tightly, but that
the presence of two K1 ions results in
mutual repulsion, hence their locations
near opposite ends of the selectivity filter.
Thus, when a second ion enters, the attractive
force between a K1 ion and the
selectivity filter becomes perfectly balanced
by the repulsive force between ions,
and this is what allows conduction to occur.
This picture accounts for both a
strong interaction between K1 ions and
the selectivity filter and a high throughput
mediated by electrostatic repulsion. On
the basis of functional measurements, the
same concept of destabilization by multiple
ion occupancy has been proposed for
Ca21 channels (22) and for K1 channels
(23) and may be a general property of all
selective ion channels.
In about 150 mM K1, the selectivity
filter contains two K1 ions (Figs. 6 and 8).
The ions are located at opposite ends of the
selectivity filter, separated by about 7.5 Å,
roughly the average distance between K1
ions in a 4 M KCl solution, and in the
selectivity filter there are no intervening
Cl2 anions to balance the charge. We
therefore conclude that the selectivity filter
attracts and concentrates K1 ions. But how
does such a selectivity filter ever conduct
ions? The structure implies that a single K1
ion would be held very tightly, but that
the presence of two K1 ions results in
mutual repulsion, hence their locations
near opposite ends of the selectivity filter.
Thus, when a second ion enters, the attractive
force between a K1 ion and the
selectivity filter becomes perfectly balanced
by the repulsive force between ions,
and this is what allows conduction to occur.
This picture accounts for both a
strong interaction between K1 ions and
the selectivity filter and a high throughput
mediated by electrostatic repulsion. On
the basis of functional measurements, the
same concept of destabilization by multiple
ผู้ได้รับการเสนอสำหรับ
ไอออนช่องทาง ca21 ( 22 ) และช่องสำหรับ K1
( 23 ) และอาจเป็นคุณสมบัติทั่วไปของ
เลือกไอออนช่องทาง
การแปล กรุณารอสักครู่..
