ISSN:
1432-1424
Keywords:
Paramecium
;
patch clamp
;
K channel
;
Ca2+ dependence
;
proteolysis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The effects of proteolysis on a hyperpolarization- and Ca2+-dependent K channel from the surface membrane ofParamecium tetraurelia were examined in the inside-out excised patch mode. Treatment with trypsin, pronase or thermolysin removed the Ca2+-dependence of the channel activation, yielding an increase in channel activity greater than 2.5-fold at all Ca2+ concentrations between 10−4 and 10−8 m. Thermolysin addition-ally removed the voltage dependence of channel opening and gave the most activation among the three proteases tested. Proteolysis did not affect the single-channel conductance. In an analogy to the mechanism of activation of many Ca2+-dependent enzymes it is suggested that thisParamecium channel has a cytoplasmic inhibitory domain which can be removed by proteolysis, and that the physiological activation by Ca2+ is due to a temporary removal of this inhibition. Moreover, these findings indicate structural differences between depolarization-, Ca2+-dependent K channels (BK channels) and the hyperpolarization-, Ca2+-dependent K channels inParamecium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01871167
