Attractants and repellents influence methylation and demethylation of methyl-accepting chemotaxis proteins in an extract of Escherichia coli.

Abstract

During bacterial chemotaxis, attractants and repellents alter the methylation levels of the methyl-accepting chemotaxis proteins (MCPs). These methylation levels represent a balance between two enzymatic processes: methylation and demethylation. In vivo experiments previously have shown that chemoeffectors influence the demethylation process; effects on the methylation system have not been reported. Here we show that in a cell-free extract of Escherichia coli both methylation and demethylation of the MCPs are affected by attractants and repellents. Attractants enhance methylation and inhibit demethylation. Repellents inhibit methylation and stimulate demethylation. The cell-free system provides an opportunity for further study of the mechanisms by which attractants and repellents influence the levels of methylation of the MCPs.As part of the mechanism of chemotaxis by Escherichia coli, attractants and repellents change the methylation levels of a set of cytoplasmic membrane proteins, the methyl-accepting chemotaxis proteins (MCPs) (1-6). These methylation levels are the result of two enzymatic processes: methyl groups are transferred from S-adenosylmethionine to the MCPs by a methylation system (7), whereas methyl groups are removed by a demethylation system to produce methanol (8,9). When the two systems are in balance, the level of methylation remains constant, but the individual methyl groups turn over (1,9,10). When an attractant is presented, the methylation level rises, and this higher value is maintained as long as the attractant is present (4). The rise coincides with a transient shut-off of demethylation (10); whether there is also an increase in methylation activity is unknown. Conversely, when a repellent is presented, the methylation level drops, and this lower value is maintained as long as the repellent is present (4). An increase in demethylation activity in response to repellents has been observed (10), but effects on methylation have not been reported.By using modifications of previously reported in vitro systems (7, 8), we have been able to examine the effects of attractants and repellents on both methylation and demethylation in a cell-free extract of E. coli. We have shown in such extracts that demethylation is inhibited by attractants and stimulated by repellents, as has been reported in intact bacteria (10). In addition, we find that methylation in these extracts is stimulated by attractants and inhibited by repellents. These results may help to explain the effects of chemoeffectors on levels of MCP methylation in intact bacteria. Nuclear. L-Arginine, L-aspartic acid, L-leucine, L-lysine, and L-serine were purchased from Calbiochem. a-Aminoisobutyric acid and a-methyl-DL-aspartic acid were obtained from Sigma.All other chemicals were reagent grade. Acetic acid, a-methylaspartic acid, and aspartic acid were used as the sodium salts.Bacteria. All strains used are E. coli K-12 derivatives and have been described previously. RP487 (9) is the chemotactically wild-type parent of AW663...

Relationships between C4 dicarboxylic acid transport and chemotaxis in Rhizobium meliloti

“…43,000 and 55,000 Da. After a 5-min incubation of E. coli with the attractant aspartate, there was a twofold increase in the label incorporated into the protein in the 55,000-Da range, consistent with previously reported increases in methyl esterification of MCPs in this organism (8,21). No equivalent increase in incorporation of label was observed in R. meliloti after exposure to either strong attractants such as cycloleucine and glutamine or moderate attractants aspartate and succinate.…”

“…Our microscopic examinations indicate that R. meliloti does adapt to strong chemotactic stimuli within 10 to 15 min. In contrast, E. coli adapts to strong attractants within a range of a few seconds to a couple of minutes, depending on the attractant concentration (21,38,42). These differences in adaptation time may reflect differences in the molecular mechanisms of adaptation.…”

“…In initial studies to determine whether protein methyl esterification is involved in R meliloti chemotaxis, as it is in E. coli (21,38,42), we examined the effects of cycloleucine on the chemotactic responsiveness, swimming behavior, and adaptation of strain JJ1c1O. Cycloleucine is a methionine analog which inhibits synthesis of S-adenosyl-Lmethionine, and hence methylation, in E. coli.…”

Chemotaxis cluster 1 proteins form cytoplasmic arrays in Vibrio cholerae and are stabilized by a double signaling domain receptor DosM

“…Changes in the duration and frequency of run and tumble phases drive a biased random walk that moves the cells toward favorable environments (5). The other response regulator, CheB, is a methylesterase, which, in conjunction with the constitutively active methyltransferase CheR, tunes the sensitivity of the system by changing the methylation state of the chemoreceptors (6)(7)(8).…”

The transmethylation and one-carbon cycle hypotheses of schizophrenia

“…In this organism a carboxymethylase has been shown to be a key factor in the development of habituation to chemical stimuli Smythies, 1980). Chemical attractants increase methylation and decrease demethylation, whereas chemical repellants have the reverse effect (Toews et al 1979;Kleene et al 1979). Transmethylation of lipids has been shown to be an essential step in many membrane reactions, including coupling of adrenergic and other receptors to adenylate cyclase, histamine release by immunoglobulin E antigens, nerve growth factor responses and others (Strittmatter et al 1979).…”