THE DEPENDENCE OF THE CONDUCTANCE OF THE HEMOCYANIN CHANNEL ON APPLIED POTENTIAL AND IONIC CONCENTRATION WITH MONO-VALENT AND DIVALENT-CATIONS

Incorporation of Megatura crenulata hemocyanin into phosphatidylcholine black lipid membranes results in the formation of ion channels. Channel properties depend on many factors, 3 of which are examined in this work: type and concentration of electrolyte and applied voltage. Eight cations [Li+, Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+] at different concentrations were used. Instantaneous conductance of the channel is a saturating function of applied voltage and ionic strength of the bathing solution with monovalent cations, but only of ionic strength with divalent cations. Steady-state voltage-conductance relations are nonlinear for both signs but show slight saturation with ionic strength. Relaxation towards the steady state can be fitted by 2 exponentials with different time constants. All experimental data are fitted postulating the existence of a mechanism of voltage gating of the channel, and of discrete negative charge near its mouth. Specific and nonspecific binding of cations is required.