Mimikakis J L, Nelson D L
Department of Biochemistry, University of Wisconsin-Madison 53706-1569, USA.
J Membr Biol. 1998 May 1;163(1):19-23. doi: 10.1007/s002329900366.
The purine nucleotide GTP causes a complex behavioral response and two distinct electrophysiological responses in the ciliated protozoan Paramecium tetraurelia. One of the two electrophysiological responses is an oscillating current that is responsible for the repeated backward swimming episodes that constitute the behavioral response to GTP. The second electrophysiological response is a sustained current whose relationship to the first is unknown. Here we show that the purine nucleotides XTP can completely block both the behavioral response to GTP and its associated oscillating current, but not the sustained current induced by GTP. Notably, XTP alone causes a sustained current similar to that induced by GTP. We believe the data support the notion that P. tetraurelia possesses two distinct signal transduction pathways sensitive to purine nucleotides: one specific for GTP that leads to oscillating currents and behavior, and a second pathway activated by GTP and other purine nucleotides that leads to a sustained current.
嘌呤核苷酸鸟苷三磷酸（GTP）在纤毛原生动物四膜虫中会引发复杂的行为反应以及两种不同的电生理反应。这两种电生理反应之一是一种振荡电流，它引发了构成对GTP行为反应的反复向后游动阶段。第二种电生理反应是一种持续电流，其与第一种电流的关系尚不清楚。在此我们表明，嘌呤核苷酸黄苷三磷酸（XTP）可以完全阻断对GTP的行为反应及其相关的振荡电流，但不能阻断GTP诱导的持续电流。值得注意的是，单独的XTP会引发一种与GTP诱导的电流类似的持续电流。我们认为这些数据支持这样一种观点，即四膜虫拥有两条对嘌呤核苷酸敏感的不同信号转导途径：一条对GTP特异，导致振荡电流和行为，另一条途径由GTP和其他嘌呤核苷酸激活，导致持续电流。
