Journal Article

How Oxygen Attacks FeFe Hydrogenases from Photosynthetic Organisms

Stripp, Sven T., Armstrong, Fraser A., Goldet, Gabrielle, Brandmayr, Caterina, Sanganas, Oliver, Vincent, Kylie A., Buchanan, Bob B., Happe, Thomas, Haumann, Michael

2009

Overview

Green algae such as Chlamydomonas reinhardtii synthesize an [FeFe] hydrogenase that is highly active in hydrogen evolution. However, the extreme sensitivity of [FeFe] hydrogenases to oxygen presents a major challenge for exploiting these organisms to achieve sustainable photosynthetic hydrogen production. In this study, the mechanism of oxygen inactivation of the [FeFe] hydrogenase CrHydAI from G reinhardtii has been investigated. X-ray absorption spectroscopy shows that reaction with oxygen results in destruction of the [4Fe-4S] domain of the active site H-cluster while leaving the di-iron domain $(2Fe_H )$essentially intact. By protein film electrochemistry we were able to determine the order of events leading up to this destruction. Carbon monoxide, a competitive inhibitor of CrHydAI which binds to an Fe atom of the $(2Fe_yH )$domain and is otherwise not known to attack FeS clusters in proteins, reacts nearly two orders of magnitude faster than oxygen and protects the enzyme against oxygen damage. These results therefore show that destruction of the [4Fe-4S] cluster is initiated by binding and reduction of oxygen at the di-iron domain—a key step that is blocked by carbon monoxide. The relatively slow attack by oxygen compared to carbon monoxide suggests that a very high level of discrimination can be achieved by subtle factors such as electronic effects (specific orbital overlap requirements) and steric constraints at the active site.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: Absorption spectroscopy / Active sites / Algae / Animals / Aquatic plants / Atoms / autotrophs / Bacterial Proteins - chemistry / Bacterial Proteins - metabolism / Biological Sciences / Carbon monoxide / Catalysis / Chlamydomonas reinhardtii / Chlamydomonas reinhardtii - metabolism / Clostridium - metabolism / Desulfovibrio / Electrochemistry / Electrochemistry - methods / Electrodes / Enzymes / Evolution / ferredoxin hydrogenase / Hydrogen / Hydrogen production / Hydrogenase / Hydrogenase - antagonists & inhibitors / Hydrogenase - chemistry / Hydrogenase - metabolism / Inactivation / iron / Iron - metabolism / Iron sulfides / Iron-Sulfur Proteins - metabolism / Kinetics / Ligands / Organisms / Oxidation / Oxygen / Oxygen - metabolism / Photosynthesis / Proteins / Spectrum analysis / X-ray absorption spectroscopy