Molecular Biology and Physiology of Platyhelminth and Algal Calcium Channels
Campbell, Christina Diane
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Calcium channels are voltage-gated, transmembrane proteins which open in response to changes in the membrane potential and allow influx of calcium ions. Insights into calcium channel and structure must provide corresponding insights into the function of the nervous system as a whole. Parasitic flatworms are logical study subjects, because they have a simple, yet completely functional neuromuscular system. If enough is discovered about the activity of their calcium channel proteins, not only will the information be helpful in learning about general nervous system function, but it would speed the synthesis of drugs that can target the nervous systems of the worms specifically enough that the hosts, whose calcium channels presumably have small but crucial structural differences, remain unharmed by the treatment. This project focused on cloning a gene coding for a calcium channel in the parasite Schistosoma mansoni. In spite of numerous attempts via PCR, 3' RACE and 5' RACE, the DNA molecule coding for the specific channel remained elusive. Preliminary physiological studies were done on the liver fluke Fasciola hepatica. Unrelated to the flatworms, yet still a valuable subject for calcium channel studies, is the freshwater green algae Chlamydomonous reinhardii. One aspect of this project involved sequencing a clone of a calcium channel gene for the organism. In Chlarnydomonous, calcium currents have been shown to be involved in regeneration of flagella. Completion of dideoxy chain termination sequencing of the gene revealed a sequence structurally similar to that of a calcium channel in the common housefly Musca domestica. This supported the previously unconfirmed hypothesis that the cloned molecule was, in fact, a gene coding for a calcium channel protein.