Spontaneous trpY mutants and mutational analysis of the TrpY archaeal transcription regulator.

Over 90% of Methanothermobacter thermautotrophicus mutants isolated as spontaneously resistant to 5-methyl tryptophan had mutations in trpY. Most were single-base-pair substitutions that identified separate DNA- and tryptophan-binding regions in TrpY. In vivo and in vitro studies revealed that DNA binding was sufficient for TrpY repression of trpY transcription but that TrpY must bind DNA and tryptophan to assemble a complex that represses trpEGCFBAD.