Bacterial chemosensory transducers are transmembrane receptor proteins that generate intracelluar signal to chemical stimuli and parcitipate in adaptation. Adaptation is linked to methylation of the specific glutamyl residues by Che R protein (methyltransferase) and also linked to demethylation of the resulting esters by Che B protein (methylesterase), which involves in deamidation of the glutaminyl residues. Trg one of chemosensory transducers mediates chemotactic responses to galactose and ribose by interacting with the sugaroccupied galactose and ribose-binding proteins. In this study, we have examined the modification patterns of 8 mutant Trg proteins, which affect flagella rotation to be biased [Clase I (CW-bias): Trg-302, Trg-301, Trg-201, Trg-303 & Class II (CCW-bias): Trg-202, Trg-304, Trg-203, Trg-305]. In che R strain, Class I Trg proteins were fully deamidated but deamidation levels of Class II Trg proteins were low. Unlike the wild type Trg protein, che Y mutation partially inhibits deamidation of the mutant Trg-201 protein. In che R che B strain which contains inactive methyltransferase and methylesterase activity, electrophoretic mobilities of two unmodified-Trg proteins, Trg-203 and Trg-303, were different from that of the wild type protein. All the mutant Trg proteins accept methyl group at amino acid position 305 (Glu) like the wild type. This suggests that the methylation at 305 residue of the Trg-201 protein requires the presence of Che B protein. It appears that in the Kl peptide of Trg, deamidation of glutaminyl residues is critical to processing of adaptation.
