title: Purification and characterization of beta-leptinotarsin-h, an activator of presynaptic calcium channels.
abstract: A new neuroactive protein, beta-leptinotarsin-h, has been purified to near-homogeneity from the hemolymph of the beetle Leptinotarsa haldemani by column chromatography. beta-Leptinotarsin-h has a molecular weight of 57 000. Rat brain synaptosomes incubated with appropriate radioactive precursors release acetylcholine (ACh), norepinephrine, and 4-aminobutyrate when exposed to beta-leptinotarin-h, but do not release lactate dehydrogenase. Release of ACh has been examined in some detail. Release of ACh varies with the concentration of beta-leptinotarsin-h in a rectangular hyperbolic fashion. Half-maximal release is stimulated by a concentration of 50 ng/mL. Altering the ionic composition of the bathing solution affects the release in a manner which suggests that neither Na+ channels nor K+ channels are affected by beta-leptinotarsin-h but that the beta-leptinotarsin-h acts to increase permeability to Ca2+. Varying the concentration of Ba2+, Sr2+, Co2+, and Cd2+ indicates that beta-leptinotarsin-h acts to open the voltage-sensitive presynaptic Ca2+ channel. beta-Leptinotarsin-h may be a useful tool for studying the Ca2+ channel associated with the release of neurotransmitters.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002413:Cations, Divalent; D066298:In Vitro Techniques; D019476:Insect Proteins; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism; D011506:Proteins / Q000302:isolation & purification* / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
chemical_list: D002413:Cations, Divalent; D019476:Insect Proteins; D007473:Ion Channels; D018377:Neurotransmitter Agents; D011506:Proteins; C023401:leptinotarsin protein, Leptinotarsa haldemani; D000109:Acetylcholine; D002118:Calcium