Proline Metabolism IncreaseskatGExpression and Oxidative Stress Resistance in Escherichia coli

• DOI: 10.1128/jb.02282-14
• Publication Date: 2014-11-11T05:10:25Z
• Authors: Lu Zhang; James R. Alfano; Donald F. Becker
• Keywords: 2. Zero hunger; 0301 basic medicine; 570; 0303 health sciences; Proline; Escherichia coli Proteins; Biophysics; Life Sciences; Gene Expression; Membrane Proteins; Catalase; Biochemistry; 3. Good health; Oxidative Stress; 03 medical and health sciences; Other Biochemistry; Bacterial Proteins; Stress, Physiological; and Structural Biology; Escherichia coli; Gene Deletion; Biotechnology

The oxidation ofl-proline to glutamate in Gram-negative bacteria is catalyzed by the proline utilization A (PutA) flavoenzyme, which contains proline dehydrogenase (PRODH) and Δ1-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 andputAmutant strains ofEscherichia coli. Initial stress assays revealed that theputAmutant strain was significantly more sensitive to oxidative stress than the parental wild-type strain. Expression of PutA in theputAmutant 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 bykatG) expression and activity. Furthermore, the ΔkatGstrain 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 ofkatGalong with several other genes involved in oxidative stress defense. In addition tokatG, proline increased the expression ofgrxA(glutaredoxin 1) andtrxC(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 inE. colivia a preadaptive effect involving endogenous hydrogen peroxide production and enhanced catalase-peroxidase activity.