Properties and regulation of the minK potassium channel protein

Abstract

The minK gene encodes a protein of 130 amino acids that has a single transmembrane segment and is expressed in many tissues including heart, uterus, and kidney. When Xenopus oocytes are injected with minK mRNA, a very slowly activating voltage-dependent potassium current is induced in these cells. The induced channels appear to result from the interaction of the minK protein with other channel-forming subunits such as the KvLQT1 channel. The minK protein is intimately associated with the structure of the resultant channels, and mutations in minK can alter ion selectivity and modulation by second messengers. Strong candidates for native currents regulated by the minK protein include the slow component of the cardiac delayed rectifier and potassium currents recorded across epithelial cells in vestibular organs and cochlea.

Sevoflurane Inhibition of the Slowly Activating Delayed Rectifier K+ Current in Guinea Pig Ventricular Cells

“…However, little is known about whether delayed rectifier K + currents, which are sensitive to volatile anesthetics, is present in the central nervous system. It has been reported that KVLQT1 is strongly expressed in human heart and pancreas (32), and KCNE1 mRNA is abundant in the kidney, submandibular gland, and the uterus (33,34). However, both are hardly expressed in the brain.…”

Cryptdin 3 forms anion selective channels in cytoplasmic membranes of human embryonic kidney cells

“…Of course, other small molecules produced in eukaryotic cells can form pores. For example, a 27-amino-acid fragment of the so-called minK potassium channel forms a cation pore by forming a homotetramer (1,18). Nonetheless, it seemed unlikely to us that one cryptdin 3 peptide could form a channel, because the size of the molecule (ϳ4 kDa) would appear to preclude a single peptide from having the multiple membrane spanning domains usually required for channel formation.…”

MinK-KvLQT1 Fusion Proteins, Evidence for Multiple Stoichiometries of the Assembled I Channel

“…I sK , or MinK, a potassium channel protein sharing little similarity with other cloned potassium channels, induces very slow voltage-dependent K ϩ channel activity in Xenopus oocytes expression system (5). It has only 130 amino acids and a single putative transmembrane domain.…”

“…Expression of MinK in Xenopus oocytes or in HEK293 cells can induce a unique slowly activating voltage-dependent K ϩ -selective current that closely resembles native I sK , the slowly activating and non-inactivating K ϩ channel current well characterized in heart (5,10). Key experiments in Xenopus oocytes suggested that the MinK protein was a regulator of expressed channel activity and not sufficient by itself to form functional I sK channels (11,12).…”