Evidence for a Paramecium folate chemoreceptor

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Abstract
Paramecium tetraurelia can detect and respond to folic acid in the environment. In order to understand the initial step in the sensory transduction process, we used covalent crosslinking of folate to determine if there were specific binding sites on the cell membrane. Crosslinked cells did not respond to folate but did respond to other chemoattractants. Membrane preparations were specifically covalently labeled with a chemically active form of folate. This labeling was detected with iodinated folate and a polyclonal antibody to folate. These results, as well as previous work from this laboratory, support the hypothesis that the folate chemical cue is transduced into a membrane potential change via a receptor.