Purinergic control of lysenin's transport and voltage-gating properties.
Lysenin, a pore-forming protein extracted from the coelomic fluid of the earthworm Eisenia foetida, manifests cytolytic activity by inserting large conductance pores in host membranes containing sphingomyelin. In the present study, we found that adenosine phosphates control the biological activity of lysenin channels inserted into planar lipid membranes with respect to their macroscopic conductance and voltage-induced gating. Addition of ATP, ADP, or AMP decreased the macroscopic conductance of lysenin channels in a concentration-dependent manner, with ATP being the most potent inhibitor and AMP the least. ATP removal from the bulk solutions by buffer exchange quickly reinstated the macroscopic conductance and demonstrated reversibility. Single-channel experiments pointed to an inhibition mechanism that most probably relies on electrostatic binding and partial occlusion of the channel-conducting pathway, rather than ligand gating induced by the highly charged phosphates. The Hill analysis of the changes in macroscopic conduction as a function of the inhibitor concentration suggested cooperative binding as descriptive of the inhibition process. Ionic screening significantly reduced the ATP inhibitory efficacy, in support of the electrostatic binding hypothesis. In addition to conductance modulation, purinergic control over the biological activity of lysenin channels has also been observed to manifest as changes of the voltage-induced gating profile. Our analysis strongly suggests that not only the inhibitor's charge but also its ability to adopt a folded conformation may explain the differences in the observed influence of ATP, ADP, and AMP on lysenin's biological activity.
Department of Physics, Boise State University, Boise, ID, 83725, USA.|Biomolecular Sciences PhD Program, Boise State University, Boise, ID, 83725, USA.
Sheenah
S
Bryant
Department of Physics, Boise State University, Boise, ID, 83725, USA.|Biomolecular Sciences PhD Program, Boise State University, Boise, ID, 83725, USA.
Nisha
N
Shrestha
Department of Physics, Boise State University, Boise, ID, 83725, USA.
Paul
P
Carnig
Department of Physics, Boise State University, Boise, ID, 83725, USA.
Samuel
S
Kosydar
Department of Physics, Boise State University, Boise, ID, 83725, USA.
Philip
P
Belzeski
Department of Physics, Boise State University, Boise, ID, 83725, USA.|Biomolecular Sciences PhD Program, Boise State University, Boise, ID, 83725, USA.
Charles
C
Hanna
Department of Physics, Boise State University, Boise, ID, 83725, USA. DanielFologea@boisestate.edu.|Biomolecular Sciences PhD Program, Boise State University, Boise, ID, 83725, USA. DanielFologea@boisestate.edu.
Daniel
0000-0002-9179-7574
D
Fologea
D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D021381:Protein Transport / Q000502:physiology; D014118:Toxins, Biological / Q000378:metabolism*
D007473:Ion Channels; D008051:Lipid Bilayers; D014118:Toxins, Biological; C107040:lysenin; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate
Adenosine phosphates; Lysenin; Pore-forming toxins; Purinergic control; Voltage gating