Eckhard Schulz

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Cyclic nucleotide-gated (CNG) ion channels mediate sensory signal transduction in photoreceptors and olfactory cells. Structurally, CNG channels are heterotetramers composed of either two or three homologue subunits. Although it is well established that activation is a cooperative process of these subunits, it remains unknown whether the cooperativity is(More)
HCN pacemaker channels are tetramers mediating rhythmicity in neuronal and cardiac cells. The activity of these channels is controlled by both membrane voltage and the ligand cAMP, binding to each of the four channel subunits. The molecular mechanism underlying channel activation and the relationship between the two activation stimuli are still unknown.(More)
Cyclic nucleotide-gated (CNG) ion channels play a key role in the sensory transduction of vision and olfaction. The channels are opened by the binding of cyclic nucleotides. Native olfactory CNG channels are heterotetramers of CNGA2, CNGA4, and CNGB1b subunits. Upon heterologous expression, only CNGA2 subunits can form functional homotetrameric channels. It(More)
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetrameric membrane proteins that generate electrical rhythmicity in specialized neurons and cardiomyocytes. The channels are primarily activated by voltage but are receptors as well, binding the intracellular ligand cyclic AMP. The molecular mechanism of channel activation is still(More)
In a multimeric receptor protein, the binding of a ligand can modulate the binding of a succeeding ligand. This phenomenon, called cooperativity, is caused by the interaction of the receptor subunits. By using a complex Markovian model and a set of parameters determined previously, we analyzed how the successive binding of four ligands leads to a complex(More)
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are voltage-gated tetrameric cation channels that generate electrical rhythmicity in neurons and cardiomyocytes. Activation can be enhanced by the binding of adenosine-3',5'-cyclic monophosphate (cAMP) to an intracellular cyclic nucleotide binding domain. Based on previously determined(More)
Tetrameric cyclic nucleotide-gated (CNG) channels mediate receptor potentials in olfaction and vision. The channels are activated by the binding of cyclic nucleotides to a binding domain embedded in the C terminus of each subunit. Here using a fluorescent cGMP derivative (fcGMP), we show for homotetrameric CNGA2 channels that ligand unbinding is ~50 times(More)
In multimeric membrane receptors the cooperative action of the subunits prevents exact knowledge about the operation and the interaction of the individual subunits. We propose a method that permits quantification of ligand binding to and activation effects of the individual binding sites in a multimeric membrane receptor. The power of this method is(More)
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetrameric proteins that evoke electrical rhythmicity in specialized neurons and cardiomyocytes. The channels are activated by hyperpolarizing voltage but are also receptors for the intracellular ligand adenosine-3',5'-cyclic monophosphate (cAMP) that enhances activation but is(More)