All aerobic organisms require mechanisms to counter the potentially damaging effects of reactive oxygen species on macromolecular cell components. Regulation of the oxidative stress response by Escherichia coli and Salmonella typhimurium is known to be coordinated at least in part by OxyR, a transcriptional activator protein capable of sensing and responding to H2O2. Our investigations focus on two proteins within the OxyR regulon, AhpF and AhpC, which together catalyze the NADH-dependent reduction of organic hydroperoxides and H2O2. Our interests in the structural and chemical bases for the enzymatic functions of these proteins rely on a wide range of approaches. Redox centers within these proteins have been identified through reductive spectral titrations; AhpF possesses bound FAD, and both proteins contain redox-active cystine disulfides. We are addressing structure-function questions as well as physiological roles of these proteins through our ability to make site-directed and deletion mutants. |
Recent Publications (selected):
Poole LB, Higuchi M, Shimada M, Calzi ML, Kamio Y.: Streptococcus mutans H2O2-forming NADH oxidase is an alkyl hydroperoxide reductase protein. Free Radic. Biol. Med. 28:108-20 (2000).
Ellis HR, Poole LB.: Novel application of 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole to identify cysteine sulfenic acid in the AhpC component of alkyl hydroperoxide reductase. Biochemistry 36:15013-8 (1997).
Li Calzi M, Poole LB.: Requirement for the two AhpF cystine disulfide centers in catalysis of peroxide reduction by alkyl hydroperoxide reductase. Biochemistry 36:13357-64 (1997).
Ellis HR, Poole LB.: Roles for the two cysteine residues of AhpC in catalysis of peroxide reduction by alkyl hydroperoxide reductase from Salmonella typhimurium. Biochemistry 36:13349-56 (1997).
|