scholarly journals Tarantula Toxins Interact with Voltage Sensors within Lipid Membranes

2007 ◽  
Vol 130 (5) ◽  
pp. 497-511 ◽  
Author(s):  
Mirela Milescu ◽  
Jan Vobecky ◽  
Soung H. Roh ◽  
Sung H. Kim ◽  
Hoi J. Jung ◽  
...  
Keyword(s):  
Ion Channels ◽  
Lipid Membranes ◽  
Voltage Sensor ◽  
Structural Motif ◽  
Membrane Interaction ◽  
Voltage Sensors ◽  
Kv Channels ◽  
Channel Interactions ◽  
The Stability ◽  
Electrical Signaling

Voltage-activated ion channels are essential for electrical signaling, yet the mechanism of voltage sensing remains under intense investigation. The voltage-sensor paddle is a crucial structural motif in voltage-activated potassium (Kv) channels that has been proposed to move at the protein–lipid interface in response to changes in membrane voltage. Here we explore whether tarantula toxins like hanatoxin and SGTx1 inhibit Kv channels by interacting with paddle motifs within the membrane. We find that these toxins can partition into membranes under physiologically relevant conditions, but that the toxin–membrane interaction is not sufficient to inhibit Kv channels. From mutagenesis studies we identify regions of the toxin involved in binding to the paddle motif, and those important for interacting with membranes. Modification of membranes with sphingomyelinase D dramatically alters the stability of the toxin–channel complex, suggesting that tarantula toxins interact with paddle motifs within the membrane and that they are sensitive detectors of lipid–channel interactions.

scholarly journals Tarantula toxins use common surfaces for interacting with Kv and ASIC ion channels

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Kanchan Gupta ◽  
Maryam Zamanian ◽  
Chanhyung Bae ◽  
Mirela Milescu ◽  
Dmitriy Krepkiy ◽  
...  
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Extracellular Domain ◽  
Voltage Sensor ◽  
Concave Surface ◽  
Voltage Sensing ◽  
Membrane Interaction ◽  
Computational Approaches ◽  
Physical Environments

Tarantula toxins that bind to voltage-sensing domains of voltage-activated ion channels are thought to partition into the membrane and bind to the channel within the bilayer. While no structures of a voltage-sensor toxin bound to a channel have been solved, a structural homolog, psalmotoxin (PcTx1), was recently crystalized in complex with the extracellular domain of an acid sensing ion channel (ASIC). In the present study we use spectroscopic, biophysical and computational approaches to compare membrane interaction properties and channel binding surfaces of PcTx1 with the voltage-sensor toxin guangxitoxin (GxTx-1E). Our results show that both types of tarantula toxins interact with membranes, but that voltage-sensor toxins partition deeper into the bilayer. In addition, our results suggest that tarantula toxins have evolved a similar concave surface for clamping onto α-helices that is effective in aqueous or lipidic physical environments.

scholarly journals TMEM266 is a functional voltage sensor regulated by extracellular Zn2+

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Ferenc Papp ◽  
Suvendu Lomash ◽  
Orsolya Szilagyi ◽  
Erika Babikow ◽  
Jaime Smith ◽  
...  
Keyword(s):  
Ion Channels ◽  
Unknown Function ◽  
Conformational Transition ◽  
Voltage Sensor ◽  
Structural Rearrangements ◽  
Future Studies ◽  
Proton Channels ◽  
Cellular Processes ◽  
Electrical Signaling ◽  
And Control

Voltage-activated ion channels contain S1-S4 domains that sense membrane voltage and control opening of ion-selective pores, a mechanism that is crucial for electrical signaling. Related S1-S4 domains have been identified in voltage-sensitive phosphatases and voltage-activated proton channels, both of which lack associated pore domains. hTMEM266 is a protein of unknown function that is predicted to contain an S1-S4 domain, along with partially structured cytoplasmic termini. Here we show that hTMEM266 forms oligomers, undergoes both rapid (µs) and slow (ms) structural rearrangements in response to changes in voltage, and contains a Zn2+ binding site that can regulate the slow conformational transition. Our results demonstrate that the S1-S4 domain in hTMEM266 is a functional voltage sensor, motivating future studies to identify cellular processes that may be regulated by the protein. The ability of hTMEM266 to respond to voltage on the µs timescale may be advantageous for designing new genetically encoded voltage indicators.

scholarly journals Cryo-EM structure of the KvAP channel reveals a non-domain-swapped voltage sensor topology

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Xiao Tao ◽  
Roderick MacKinnon
Keyword(s):  
Ion Channels ◽  
Conformational Changes ◽  
Voltage Sensor ◽  
Structural Domains ◽  
Structural Class ◽  
Voltage Sensors ◽  
Voltage Gated ◽  
Voltage Dependent ◽  
Voltage Gated Ion Channels ◽  
Gated Ion Channels

Conductance in voltage-gated ion channels is regulated by membrane voltage through structural domains known as voltage sensors. A single structural class of voltage sensor domain exists, but two different modes of voltage sensor attachment to the pore occur in nature: domain-swapped and non-domain-swapped. Since the more thoroughly studied Kv1-7, Nav and Cav channels have domain-swapped voltage sensors, much less is known about non-domain-swapped voltage-gated ion channels. In this paper, using cryo-EM, we show that KvAP from Aeropyrum pernix has non-domain-swapped voltage sensors as well as other unusual features. The new structure, together with previous functional data, suggests that KvAP and the Shaker channel, to which KvAP is most often compared, probably undergo rather different voltage-dependent conformational changes when they open.

scholarly journals The AMIGO1 adhesion protein modulates movement of Kv2.1 voltage sensors

2021 ◽  
Author(s):  
Rebecka J Sepela ◽  
Robert G Stewart ◽  
Luis Valencia ◽  
Parashar Thapa ◽  
Zeming Wang ◽  
...  
Keyword(s):  
Neuronal Excitability ◽  
Voltage Sensor ◽  
Charge Voltage ◽  
Adhesion Protein ◽  
Voltage Sensors ◽  
Kv Channels ◽  
Mammalian Cell Lines ◽  
Fluorescence Measurements ◽  
Gating Charge ◽  
And Shifts

Voltage-gated potassium (Kv) channels sense voltage and facilitate transmembrane flow of K+ to control the electrical excitability of cells. The Kv2.1 channel subtype is abundant in most brain neurons and its conductance is critical for homeostatic regulation of neuronal excitability. Many forms of regulation modulate Kv2.1 conductance, yet the biophysical mechanisms through which the conductance is modulated are unknown. Here, we investigate the mechanism by which the neuronal adhesion protein AMIGO1 modulates Kv2.1 channels. With voltage clamp recordings and spectroscopy of heterologously expressed Kv2.1 and AMIGO1 in mammalian cell lines, we show that AMIGO1 modulates Kv2.1 voltage sensor movement to change Kv2.1 conductance. AMIGO1 speeds early voltage sensor movements and shifts the gating charge-voltage relationship to more negative voltages. Fluorescence measurements from voltage sensor toxins bound to Kv2.1 indicate that the voltage sensors enter their earliest resting conformation, yet this conformation is less stable upon voltage stimulation. We conclude that AMIGO1 modulates the Kv2.1 conductance activation pathway by destabilizing the earliest resting state of the voltage sensors.

scholarly journals Dimer interaction in the Hv1 proton channel

2020 ◽  
Vol 117 (34) ◽  
pp. 20898-20907
Author(s):  
Laetitia Mony ◽  
David Stroebel ◽  
Ehud Y. Isacoff
Keyword(s):  
Functional Analysis ◽  
Ion Channel ◽  
Coiled Coil ◽  
Voltage Sensor ◽  
Proton Channel ◽  
Dimer Interface ◽  
Voltage Sensors ◽  
Voltage Gated ◽  
Channel Opening ◽  
The Stability

The voltage-gated proton channel Hv1 is a member of the voltage-gated ion channel superfamily, which stands out in design: It is a dimer of two voltage-sensing domains (VSDs), each containing a pore pathway, a voltage sensor (S4), and a gate (S1) and forming its own ion channel. Opening of the two channels in the dimer is cooperative. Part of the cooperativity is due to association between coiled-coil domains that extend intracellularly from the S4s. Interactions between the transmembrane portions of the subunits may also contribute, but the nature of transmembrane packing is unclear. Using functional analysis of a mutagenesis scan, biochemistry, and modeling, we find that the subunits form a dimer interface along the entire length of S1, and also have intersubunit contacts between S1 and S4. These interactions exert a strong effect on gating, in particular on the stability of the open state. Our results suggest that gating in Hv1 is tuned by extensive VSD–VSD interactions between the gates and voltage sensors of the dimeric channel.

scholarly journals Opening the Shaker K+ channel with hanatoxin

2013 ◽  
Vol 141 (2) ◽  
pp. 203-216 ◽  
Author(s):  
Mirela Milescu ◽  
Hwa C. Lee ◽  
Chan Hyung Bae ◽  
Jae Il Kim ◽  
Kenton J. Swartz
Keyword(s):  
K Channel ◽  
Voltage Sensors ◽  
Channel Interaction ◽  
Kv Channel ◽  
Kv Channels ◽  
Structural Details ◽  
In The Wild ◽  
Protein Toxins ◽  
Electrical Signaling ◽  
Voltage Relationship

Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1–S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1–S4 domain and inhibits opening by stabilizing a closed state. Here we investigated the interaction of hanatoxin with the Shaker Kv channel, a voltage-activated channel that has been extensively studied with biophysical approaches. In contrast to what is observed in the Kv2.1 channel, we find that hanatoxin shifts the conductance–voltage relation to negative voltages, making it easier to open the channel with membrane depolarization. Although these actions of the toxin are subtle in the wild-type channel, strengthening the toxin–channel interaction with mutations in the S3b helix of the S1-S4 domain enhances toxin affinity and causes large shifts in the conductance–voltage relationship. Using a range of previously characterized mutants of the Shaker Kv channel, we find that hanatoxin stabilizes an activated conformation of the voltage sensors, in addition to promoting opening through an effect on the final opening transition. Chimeras in which S3b–S4 paddle motifs are transferred between Kv2.1 and Shaker Kv channels, as well as experiments with the related tarantula toxin GxTx-1E, lead us to conclude that the actions of tarantula toxins are not simply a product of where they bind to the channel, but that fine structural details of the toxin–channel interface determine whether a toxin is an inhibitor or opener.

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