The influence of ATP on the binding of aromatic amino acids to the ligand response domain of the tyrosine repressor of Haemophilus influenzae

Abstract

The binding of aromatic amino acids to the ligand response domain of the tyrosine repressor (TyrR) protein (TyrR_lrd) of Haemophilus influenzae was investigated using circular dichroism and fluorescence spectroscopy. The induced secondary structural changes were unique for each aromatic amino acid and were further influenced by the presence or absence of ATP. Tyrosine was found to have the highest affinity for TyrR_lrd in the absence of ATP, whereas the affinity for ATP itself increased in the presence of tyrosine. Binding of tyrosine is therefore the conformational trigger for the activation of TyrR whereas ATP is regarded as a conformational co‐activator.