a) Ion Selectivity: The selectivity filter is the structural feature of K+ channels that accounts for ion selectivity. This filter is located at the narrowest part of the pore and is composed of the backbone carbonyl oxygens from the K+ channel protein. These oxygens mimic the hydration shell of the K+ ion, allowing it to shed its waters of hydration and pass through the filter. The selectivity filter is highly selective for K+ ions over Na+ ions due to the precise arrangement of the carbonyl oxygens, which matches the diameter and hydration energy of the K+ ion.

b) Voltage Sensitivity: The voltage-sensing domain (VSD) is the structural feature of K+ channels that accounts for voltage sensitivity. The VSD is composed of four transmembrane segments (S1-S4), with the S4 segment containing multiple positively charged residues. Changes in membrane potential cause these charged residues to move, leading to conformational changes in the channel that open or close the pore.

c) Ion Conductance: The pore domain is the structural feature of K+ channels that accounts for ion conductance. This domain forms the central pathway for ion flow through the membrane. The size and shape of the pore, as well as the properties of the amino acids lining the pore, determine the rate of ion flow (conductance) through the channel. The pore is wide enough to allow rapid flow of K+ ions but narrow enough to prevent flow of larger ions or molecules.

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a) Ion Selectivity: The selectivity filter is the structural feature of K+ channels that accounts for ion selectivity. This filter is located at the narrowest part of the pore and is composed of the backbone carbonyl oxygens from the K+ channel protein. These oxygens mimic the hydration shell of the K+ ion, allowing it to shed its waters of hydration and pass through the filter. The selectivity filter is highly selective for K+ ions over Na+ ions due to the precise arrangement of the carbonyl oxygens, which matches the diameter and hydration energy of the K+ ion.

b) Voltage Sensitivity: The voltage-sensing domain (VSD) is the structural feature of K+ channels that accounts for voltage sensitivity. The VSD is composed of four transmembrane segments (S1-S4), with the S4 segment containing multiple positively charged residues. Changes in membrane potential cause these charged residues to move, leading to conformational changes in the channel that open or close the pore.

c) Ion Conductance: The pore domain is the structural feature of K+ channels that accounts for ion conductance. This domain forms the central pathway for ion flow through the membrane. The size and shape of the pore, as well as the properties of the amino acids lining the pore, determine the rate of ion flow (conductance) through the channel. The pore is wide enough to allow rapid flow of K+ ions but narrow enough to prevent flow of larger ions or molecules.

Knowee AI · Accepted Answer

a) Ion Selectivity: The selectivity filter is the structural feature of K+ channels that accounts for ion selectivity. This filter is located at the narrowest part of the pore and is composed of the backbone carbonyl oxygens from the K+ channel protein. These oxygens mimic the hydration shell of the K+ ion, allowing it to shed its waters of hydration and pass through the filter. The selectivity filter is highly selective for K+ ions over Na+ ions due to the precise arrangement of the carbonyl oxygens, which matches the diameter and hydration energy of the K+ ion.

b) Voltage Sensitivity: The voltage-sensing domain (VSD) is the structural feature of K+ channels that accounts for voltage sensitivity. The VSD is composed of four transmembrane segments (S1-S4), with the S4 segment containing multiple positively charged residues. Changes in membrane potential cause these charged residues to move, leading to conformational changes in the channel that open or close the pore.

c) Ion Conductance: The pore domain is the structural feature of K+ channels that accounts for ion conductance. This domain forms the central pathway for ion flow through the membrane. The size and shape of the pore, as well as the properties of the amino acids lining the pore, determine the rate of ion flow (conductance) through the channel. The pore is wide enough to allow rapid flow of K+ ions but narrow enough to prevent flow of larger ions or molecules.

Which structural features of K+ channels account for: a) ion selectivity, b) voltage sensitivity, and c) ion conductance?

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