GENETIC ANALYSIS OF MUTANTS WITH A REDUCED Ca²⁺-DEPENDENT K⁺ CURRENT IN PARAMECIUM TETRAURELIA

Robert D. Hinrichsen ¹, Ed Amberger ¹, Yoshiro Saimi ¹, Anthony Burgess-Cassler ¹, and Ching Kung ²

¹ Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706
² Laboratory of Molecular Biology and Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706

Two mutants of Paramecium tetraurelia with greatly reduced Ca²⁺-dependent K⁺ currents have been isolated and genetically analyzed. These mutants, designated pantophobiac, give much stronger behavioral responses to all stimuli than do wild-type cells. Under voltage clamp, the Ca²⁺-dependent K⁺ current is almost completely eliminated in these mutants, whereas the Ca²⁺ current is normal. The two mutants, pntA and pntB, are recessive and unlinked to each other. pntA is not allelic to several other ion-channel mutants of P. tetraurelia. The microinjection of a high-speed supernatant fraction of wild-type cytoplasm into either pantophobiac mutant caused a temporary restoration to the wild-type phenotype.

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