The protein kinase, CheA, plays a central role in the initial excitation responses to stimuli as well as in the subsequent events associated with adaptation. The activity of the CheA kinase is increased by the increased levels
of receptor methylation . High levels of receptor methylation have been correlated with tumbly behavior, providing evidence that changes in receptor methylation mediate adaptive responses to attractant and repellent stimuli. Thus, the increased expression of these genes is closely related to negative Ada-dependent regulation in E. coli and Ada might negatively affect the protein components of bacterial chemotaxis. The flagellar biosynthesis genes and chemotaxis genes seem to contribute to protecting the viability of ada mutant cells by transferring methyl
group to methyl-accepting proteins (MCP) such as Aer, Tar and Trg. Increased expression levels of the genes and proteins related to drugs PF-01367338 purchase or www.selleckchem.com/products/Flavopiridol.html antibiotics resistance The ada mutant cells that are hypersensitive to alkylating agents compared to wild-type cells might need to activate the expression of drug or antibiotic resistance genes to reduce their susceptibility to alkylation damage. In fact, many genes involved in these functions were found to be induced, some rapidly and some later in response to buy PCI-32765 MMS treatment (Figure 4). The expression level of the fsr gene responsible for fosmidomycin resistance was rapidly and continuously induced in both strains after MMS treatment, and this gene selleck screening library also showed increased expression in the ada mutant strain compared to the wild-type under normal growth condition. Additionally, genes encoding the multiple antibiotic resistance protein (marABR), microcin B17 uptake protein (sbmA), and putative resistance protein (ydeA) were also up-regulated in both strains at 3.9 h post MMS treatment, in the stationary phase. This observation
is consistent with the fact that the Ada regulon is highly induced during the stationary phase  and that it protects cells from active alkylators produced by nitrosation of amino acids [1, 2]. However, some of genes belonging to this function showed different expression patterns between the strains. For example, the genes encoding multidrug resistance proteins (emrABDE) were rapidly induced at 0.5 h profile in the ada mutant strain and decreased afterwards. On the other hand, some of these genes (emrBEY) were increased later at 3.9 h profile only in the wild-type strain. This result suggests that the ada mutant strain might require a timely and rapid induction of the drug or antibiotic resistance genes to reduce its susceptibility to alkylation damage. Proteome data also showed induction of proteins related to detoxification (AhpF and NfnB) in both strains following MMS treatment. Alkylating agents that target DNA-associated processes are anticipated to be far more specific and effective as antibiotics or drugs [3–5].