TAILIEUCHUNG - Báo cáo khoa học: Enlarging the gas access channel to the active site renders the regulatory hydrogenase HupUV of Rhodobacter capsulatus O2 sensitive without affecting its transductory activity

In the photosynthetic bacterium Rhodobacter capsulatus, the synthesis of the energy-producing hydrogenase, HupSL, is regulated by the substrate H2, which is detected by a regulatory hydrogenase, HupUV. The HupUV protein exhibits typical features of [NiFe] hydrogenases but, interestingly, is resistant to inactivation by O2. Understanding the O2 resistance of HupUV will help in the design of hydrogenases with high potential for bio-technological applications. | ềFEBS Journal Enlarging the gas access channel to the active site renders the regulatory hydrogenase HupUV of Rhodobacter capsulatus O2 sensitive without affecting its transductory activity Ophelie Duche1 Sylvie Elsen1 Laurent Cournac2 and Annette Colbeau1 1 Laboratoire de Biochimie et Biophysique des Systemes Integres UMR 5092 CNRS-CEA-UJF Departement Reponse et Dynamique Cellulaires Grenoble France 2 CEA Cadarache Departement des Sciences du Vivant Departement d Ecophysiologie Vegetale et de Microbiologie Laboratoire d Ecophysiologie de la Photosynthese UMR 6191 CNRS-CEA-Aix Marseille II Saint Paul-lez-Durance France Keywords gas access channel hydrogenases oxygen sensitivity Rhodobacter capsulatus Correspondence A. Colbeau Laboratoire de Biochimie et Biophysique des Systemes Integres DRDC CEA Grenoble 17 rue des martyrs 38054 Grenoble Cedex 9 France Fax 33 4 38 78 51 85 Tel 33 4 38 78 30 74 E-mail umr5092@ Website http bbsi Received 13 May 2005 revised 26 May 2005 accepted 6 June 2005 doi In the photosynthetic bacterium Rhodobacter capsulatus the synthesis of the energy-producing hydrogenase HupSL is regulated by the substrate H2 which is detected by a regulatory hydrogenase HupUV. The HupUV protein exhibits typical features of NiFe hydrogenases but interestingly is resistant to inactivation by O2. Understanding the O2 resistance of HupUV will help in the design of hydrogenases with high potential for biotechnological applications. To test whether this property results from O2 inaccessibility to the active site we introduced two mutations in order to enlarge the gas access channel in the HupUV protein. We showed that such mutations Ile65 fi Val and Phe113 fi Leu in HupV rendered HupUV sensitive to O2 inactivation. Also in contrast with the wild-type protein the mutated protein exhibited an increase in hydrogenase activity after reductive activation in the presence of reduced methyl viologen up to 30 of

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