Proline metabolism increases katG expression and oxidative stress resistance in Escherichia coli.
The oxidation of l-proline to glutamate in Gram-negative bacteria is catalyzed by the proline utilization A (PutA) flavoenzyme, which contains proline dehydrogenase (PRODH) and Δ(1)-pyrroline-5-carboxylate (P5C) dehydrogenase domains in a single polypeptide. Previous studies have suggested that aside from providing energy, proline metabolism influences oxidative stress resistance in different organisms. To explore this potential role and the mechanism, we characterized the oxidative stress resistance of wild-type and putA mutant strains of Escherichia coli. Initial stress assays revealed that the putA mutant strain was significantly more sensitive to oxidative stress than the parental wild-type strain. Expression of PutA in the putA mutant strain restored oxidative stress resistance, confirming that depletion of PutA was responsible for the oxidative stress phenotype. Treatment of wild-type cells with proline significantly increased hydroperoxidase I (encoded by katG) expression and activity. Furthermore, the ΔkatG strain failed to respond to proline, indicating a critical role for hydroperoxidase I in the mechanism of proline protection. The global regulator OxyR activates the expression of katG along with several other genes involved in oxidative stress defense. In addition to katG, proline increased the expression of grxA (glutaredoxin 1) and trxC (thioredoxin 2) of the OxyR regulon, implicating OxyR in proline protection. Proline oxidative metabolism was shown to generate hydrogen peroxide, indicating that proline increases oxidative stress tolerance in E. coli via a preadaptive effect involving endogenous hydrogen peroxide production and enhanced catalase-peroxidase activity.
Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, USA Redox Biology Center, University of Nebraska, Lincoln, Nebraska, USA.
Lu
L
Zhang
Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska, USA Redox Biology Center, University of Nebraska, Lincoln, Nebraska, USA Center for Plant Science Innovation, University of Nebraska, Lincoln, Nebraska, USA.
James R
JR
Alfano
Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, USA Redox Biology Center, University of Nebraska, Lincoln, Nebraska, USA dbecker3@unl.edu.
Donald F
DF
Becker
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002374:Catalase / Q000096:biosynthesis* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000235:genetics; D017353:Gene Deletion; D015870:Gene Expression; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D011392:Proline / Q000378:metabolism*; D013312:Stress, Physiological
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C080683:PutA protein, Bacteria; D011392:Proline; D002374:Catalase; C051253:katG protein, E coli