ArsH from the CyanobacteriumSynechocystissp. PCC 6803 Is an Efficient NADPH-Dependent Quinone Reductase

• DOI: 10.1021/bi201904p
• Publication Date: 2012-01-23T20:36:15Z
• Authors: Manuel Hervás; Luis López-Maury; Pilar León; Ana M. Sánchez-Riego; Francisco J. Flor...; José A. Navarro
• Keywords: Semiquinone; Synechocystis; Flavin mononucleotide; Electron acceptor

The cyanobacterium Synechocystis sp. PCC 6803 possesses an arsenic resistance operon that encodes, among others, ArsH protein. is a flavin mononucleotide (FMN)-containing protein of unknown function and member the family NADPH-dependent FMN reductases. nature its final electron acceptor role in to remained be clarified. Here we have expressed purified conducted intensive biochemical study. We present kinetic evidence supporting quinone reductase activity for ArsH, with preference quinones hydrophobic substituents. By using steady-state measurements, as well stopped-flow laser-flash photolysis analyses, it has been possible establish mechanism process estimate values constants. Although enzyme able stabilize anionic semiquinone form FMN, reduction involves hydroquinone cofactor, enzymatic reaction occurs through ping-pong-type mechanism. catalyze one-electron reactions (oxygen cytocrome c reduction), involving form, but lower efficiency. In addition, arsH mutants are sensitive oxidizing agent menadione, suggesting plays response oxidative stress caused by arsenite.