This thesis details a study of the GST's found in 2 sibling strains of corn, GT112 and GT112 RfRf. These strains differ in their atrazine-specific GST activity. There is probably a minimum of 5 GST's in corn: GST I, GST II (not included in this work), GST III, and 2 GST's with activity against atrazine. A new purification scheme for GST I and GST III from corn leaves has been developed, utilizing an Orange A column as an affinity column. GST I and a mix of GST I and III were used for determination of N-terminal amino acid sequences and for raising antibodies. The N-terminal sequences allowed the enzymes to be identified as GST I and GST III (Shah et al., 1986; Moore et al., 1986). Western blots show that the GST I antibody had some cross-reactivity with GST III. The purified mixture of GST I and III contained a minor amount of atrazine-GST activity compared to the total atrazine-GST activity. The atrazine-GST activity was partially purified, but the activity was lost before a single protein could be isolated. Based on size and presence in partially purified but still active samples, a suspect 25.5 kDa protein was purified and used to generate antibodies. This antibody, the GST I antibody, and the GST I/III antibody were unable to block partially purified atrazine-GST activity. The possible identification of this 25.5 kDa protein as an atrazine-specific GST was further questioned by the fact that the atrazine-GST activity eluted from a native gel appeared to migrate faster than the 25.5 kDa protein. The 25.5 kDa protein antibody was also used to screen a GT112 cDNA library, and a similar GT112 RfRf library constructed by Greg Grove. Two classes of clones were isolated and partially sequenced, but there was no evidence that they code for GST's. Nevertheless, this work has shown that the atrazine-specific GST has very little, if any CDNB-GST activity. The use of CDNB as a universal substrate for GST's is, therefore, not always correct since CDNB assays may not detect all GST's.
