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potassium voltage-gated channel, subfamily H (eag-related), member 6
The voltage-gated K+ channels of the EAG (ether-à-go-go) family consist of three subfamilies: eag, elk (eag-like) and erg (eag-related gene). Erg channels play critical roles in regulating the resting membrane potential , , action potential duration , spike frequency adaptation  and hormone secretion . Due to a Per-Arnt-Sim domain in the N-terminus of erg channel subunits, even a role in O2-sensing has been discussed . The different physiological roles of erg channels are enabled by their peculiar gating . The erg subfamily consists of three members: erg1, erg2 (aka. Kv11.2) and erg3 , , . These subunits may form homomultimeric channels, but they are also able to form heteromultimers within their subfamily .
Kcnh6 : potassium voltage-gated channel, subfamily H (eag-related), member 6
Erg1 and Erg3
In the central nervous system of mammals, two other ERG channel genes are expressed (ERG2 and ERG3)11, and here heteromultimeric channel complexes of all three subunits can be formed 
RPR regulates hERG1 and rERG2 differentially
RPR260243 (RPR) induces voltage-dependent slowing of hERG1 deactivation. A study using site-directed mutagenesis proposed the C-linker domain as key component of slow deactivation in ERG channels and found that residues in the C-linker and the adjacent cyclic nucleotide-binding homology domains are sufficient to explain the different sensitivities of hERG1 and rERG2 to RPR.
Schematic diagram of Kv11.2
Schematic diagram of a Kv11 subunit containing six alpha-helical transmembrane segments S1–S6 (in gray) and the pore P. The locations of the N-terminal PAS- domain and the C-terminal cyclic nucleotide binding domain (CNBD) are highlighted in dark and light blue, respectively. 
The ether-a-go-go gene K+ channel alpha-subunits consist of six membrane-spanning domains (S1–S6). A Per-Arnt-Sim (PAS) domain is located at the N-terminus and a cyclic nucleotide-binding domain (cNBD) in the C-terminus. This, and the tetrameric structure of a K+ channel can be seen in fig1 of Bauer . The pore region P and S6 may form the inner core of the channel, S1–S5 the outer parts of the channel with S4 as the voltage sensor. 
Drug Binding Site to hERG channel
The side chains of all four residues are orientated towards the large central cavity of the channel, which is consistent with the observation that hERG channels are only blocked by these drugs after the channel has opened. The two pore helix residues (Thr 623 and Ser 624) are highly conserved in Kv channels and thus cannot easily explain the promiscuous blocking by drugs of hERG. However, the two S6 residues (Tyr 652 and Phe 656) are not conserved — most Kv channels have an Ile and a Val in homologous positions. Further mutagenesis identified the most relevant physicochemical properties of these two S6 residues 
Kv11.2 Distribution in Neuronal Retina
In contrast to this postsynaptic distribution of Kv11.1 subunits in the OPL, Kv11.2 seemed to be expressed presynaptically in this layer (see Fig. 2B). The additional occurrence of Kv11.2 in dense packages in the IPL indicates the expression of Kv11.2 subunits presynaptically in ribbon synapses of both, photoreceptors and bipolar cells. As these synapses are glutamatergic, we performed double-labeling experiments with Kv11.2- and vGluT1-specific antibodies 
Expression in CNS
Kv11.2 and Kv11.3 are thought, contrary to Kv11.1, to be found exclusively in the nervous system . However, recently, Kv11.2 and Kv11.3 transcripts were shown in rat pancreatic islets . In rodent brain, the three channel subtypes display a widespread expression pattern although one study did detect Kv11.2 almost exclusively in the olfactory bulb 
Herg channel expression in Brain
All three Kv11 channels are expressed in the olfactory bulb, and erg1 and erg3 are co-expressed in the reticular thalamic nucleus, cerebral cortex, cerebellum and hippocampus . Single cell RT-PCR experiments have shown that the erg subunits can be expressed in different combinations in individual rat lactotroph cells . In addition, transcripts for more than one erg subunit have been detected in various cell lines: NG108-15 (neuroblastoma, erg1–3, ), PC12 (sympathetic ganglia neuron, erg1 and erg2, ), MMQ (lactotroph, erg1–3, ) and GH3/B6 (somatomammotroph, erg1 and erg2, ).
Expression in Rat
Kv11.2 and Kv11.3 are thought, contrary to Kv11.1, to be found exclusively in the nervous system . However Kv11.2 and Kv11.3 transcripts were shown in rat pancreatic islets . In rodent brain, the three channel subtypes display a widespread expression pattern , , . although one study  did detect Kv11.2 almost exclusively in the olfactory bulb. (From )
By real-time PCR experiments we were able to show that Kv11.1 and Kv11.2 are expressed in a comparable level in the mouse retina while Kv11.3 expression was significantly lower 
Pre vertebral Sympathetic Ganglia
The erg2 gene is expressed abundantly in the two prevertebral sympathetic ganglia examined: the celiac ganglia (CG) and the superior mesenteric ganglia (SMG) 
Tissue distribution of herg2
Neither erg2 nor erg3 mRNA is expressed at detectable levels in atrial or ventricular (Vent) muscle, 
Kv11.2 channels are expressed presynaptically in glutamatergic synapses of the retina, suggesting their contribution to the synaptic release of glutamate in photoreceptors and bipolar cells. The axons of OFF bipolar cells terminate in the outer half of the IPL, whereas those of ON and rod bipolar cells terminate in the inner half of the IPL. Accordingly, the co-localization of Kv11.2 and vGluT1 throughout the IPL strongly suggests that Kv11.2 subunits are expressed in all types of bipolar cells, but not in amacrine cells which is supported by the absence of Kv11.2 and GAD65 co-staining 
Kinetics of human fetal Kv11.2 in X. oocytes
 Voltage dependence of channel activation (-80mV) to Peak (60mV). The activation rate was voltage dependent for all three Kv11 channels, the activation rate being faster at more depolarized potentials. Kv11.2 activated more than twofold slower than hKv11.1.
Like eag1 currents, eag2 currents exhibit a pronounced Cole-Moore shift and they are blocked by low concentrations of cytosolic Ca2+ , . However, the activation threshold of eag2 channels is much more negative (−100 mV) than that of rat eag1 channels (−50 mV), and eag2 channels exhibit only a weak potential dependence. 
Rat Kv11.2 (erg2) Expressed in CHO cells
The different erg subunits vary considerably in their expression levels (compare erg1 and erg2 in the figure where erg2 cDNA was injected in a ten-fold concentration compared with erg1). Therefore, we concatenated two erg subunits by cloning the 5'-end of one cDNA to the 3'-end of the other one to obtain homogeneous channel populations with a defined subunit composition. The strongest inward rectifier were erg2 channels when compared to erg1 and erg3 
Activation curves of Erg1a, Erg1b, Erg2 (Kv11.2) and Erg3 channels
Voltage dependence of Erg current activation and inactivation in Purkinje cells compared to currents of Erg1a, Erg1b, Erg2 and Erg3 channels heterologously expresssed in HEK293 cells. Activation curves of erg1b and erg2 were shifted to more positive potentials by ∼20 and >40 mV, respectively, compared to erg1a and erg3 currents.