Betaine aldehyde dehydrogenase from Pseudomonas aeruginosa: cloning, over-expression in Escherichia coli, and regulation by choline and salt

Abstract

In the human pathogen Pseudomonas aeruginosa, betaine aldehyde dehydrogenase (BADH) may play a dual role assimilating carbon and nitrogen from choline or choline precursors--abundant at infection sites--and producing glycine betaine, which protects the bacteria against the high-osmolarity stress prevalent in the infected tissues. We cloned the P. aeruginosa BADH gene and expressed the BADH protein in Escherichia coli. The recombinant protein appears identical to its native counterpart, as judged by Western blot, N-terminal amino acid sequence, tryptophan-fluorescence emission spectra, circular-dichroism spectroscopy, size-exclusion chromatography, and kinetic properties. Computational analysis indicated that the promoter sequence of the putative operon that includes the BADH gene has a consensus-binding site for the choline-sensing transcription repressor BetI, and putative boxes for ArcA and Lrp transcription factors but no known elements of response to osmotic stress. This is consistent with the strong induction of BADH expression by choline and with the lack of effect of NaCl. As there were significant amounts of BADH protein and activity in P. aeruginosa cells grown on glucose plus choline, as well as the BADH activity exhibiting tolerance to salt, it is likely that glycine betaine is synthesized in vivo and could play an important osmoprotectant role under conditions of infection.

Choline Catabolism in Burkholderia thailandensis Is Regulated by Multiple Glutamine Amidotransferase 1-Containing AraC Family Transcriptional Regulators

“…The choline catabolic pathway and its regulation in P. aeruginosa have been described previously (20,22). Briefly, in P. aeruginosa the TetR family transcription factor BetI represses expression of betIBA and is derepressed by choline, allowing production of the BetA and BetB enzymes that convert choline into GB (39)(40)(41). The GATase 1-like AraC family transcription regulator (GATR) GbdR responds to GB and dimethylglycine (DMG) by inducing expression of catabolic genes, including gbcA-B, the dgc operon (PA5376, PA5377, dgcA, dgcB, PA5400, and PA5401), and the sarcosine oxidase genes, which together contribute to the sequential demethylation of GB to DMG, sarcosine, and finally glycine ( Fig.…”

Anr and Its Activation by PlcH Activity in Pseudomonas aeruginosa Host Colonization and Virulence

“…A recent study has shown that P. aeruginosa betI and betB transcripts were particularly upregulated in CF patient lung infections, as well as burn wound samples, compared to those in planktonic controls (56). Because the betaine aldehyde dehydrogenase-encoding genes are responsible for the conversion of choline to GB (57), this implies choline uptake and utilization in vivo.…”

Homeostasis and Catabolism of Choline and Glycine Betaine: Lessons from Pseudomonas aeruginosa

“…In most bacteria, one of the BCCT-family transporters is close to, and generally divergently transcribed from, the choline oxidase genes and its associated choline-responsive transcription factor (51-53). In P. aeruginosa, this transporter is named BetT1, and it is divergently transcribed from the betIBA operon, where betI encodes the BetI choline-responsive transcriptional repressor (53,54) (Fig. 2).…”

“…First, loss of BetI repression leads to betT1 induction (48), which provides for a higher rate of choline transport when choline remains in the extracellular environment. Second, loss of BetI repression stimulates transcription of betIBA, a single polycistronic transcript encoding the BetI repressor and the BetA and BetB enzymes for oxidation of choline to GB (52,53,89) (Fig. 2).…”