Worm Breeder's Gazette 9(1): 47
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
The cn101 mutation that was originally isolated as a temperature dependent paralytic mutant, was found to be an allele of the cha-1 gene, the structural gene for choline acetyltransferase (ChAT). The strain is normal in its phenotypes (development, behavior and drug sensitivity) at 16 C but abnormal at restrictive temperature : slow growth and small adult size at 25 C, resistance to cholinesterase inhibitors and paralysis by coiling its body at 30 C. J. B. Rand mapped many alleles of genes cha-1 and unc-17. The relative position of the cn101 mutation was determined based on complementation for behavioral deficiency with available markers as follows (distances between markers are arbitrarily positioned). [See Figure 1] ChAT activity of crude extracts from cn101 grown at permissive temperature (16 C) was only 10% of wild-type ChAT activity. ChAT from the mutant was very temperature sensitive that is, the activity was maximal at 10 C but not detectable at 25 C, while wild-type enzyme activity was maximal at 25 C. In order to know the relationship between paralytic behavior and enzyme level caused by this mutation, we purified the mutant ChAT about 80-fold using (NH4)2SO4 fractionation, Sephacryl and DEAE chromatography. The partially purified enzyme was still temperature sensitive as in the crude enzyme. The differences between both enzymes in the affinity for choline and acetyl-CoA were not remarkable. However, the affinities for the substrates were greatly reduced by high concentration of NaCl in the mutant enzyme as summerized below. These results are consistent with that cn101 is the mutation of the structural gene for ChAT whose activity is greatly affected by temperature and salt concentration.