Functional structure of the repressor protein of the Bacillus subtilis gny operon

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The head investigator (me) has been studied this subject for last 6years. Among the fruitful achievements on the subject, the results of analysis for the binding domain of the gnt repressor protein (J.Basteriol. 177 : 4813) and those of analysis for interaction of this repressor and the gnt operator (Mol. Gen. Genet. 248 : 583) have been published in 1995after conduct of some additional experiments. In last two years, I have attempted to crystallize the gnt repressor for X-ray analysis under various crystallization conditions. I have also tried to crystallize the purified mutant repressors defective in operator binding. However, I could obtain no crystalline suitable for X-ray analysis but small needle-like one. Therefore, I concluded that the gnt repressor was hard to be crystallized because its tendency to polymerize at the high concentration. Meanwhile, I have analyzed details of kinetics of interaction between the gnt repressor and inducer by means of filter-binding method. I found that although the repressor lost the binding ability to the operator in the presence of the inducer (gluconate or glucono-delta-lacton), it gained a non-specific DNA binding ability. This binding ability was specifically induced in the presence of gluconate or glucono-delta-lacton. I am currently investigating the physiological significance for induction of this non-specific DNA binding. A few years ago, it has been proposed that a new subfamily of bacterial regulatory proteins represented by this gnt repressor protein (GntR family). Nowadays, the GntR family of bacterial regulatory proteins is internationally agreed, the members of which rapidly increased in the recent progress of the sequencing of several bacterial geneomes. I collected information about the functions of the members of the GntR family from the protein databases and classified them according to their functions.