Light-driven oxygen production from superoxide by Mn-binding bacterial reaction centers

James Allen, Tien L. Olson, Paul Oyala, Wei Jen Lee, Aaron A. Tufts, Joann Williams

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

One of the outstanding questions concerning the early Earth is how ancient phototrophs made the evolutionary transition from anoxygenic to oxygenic photosynthesis, which resulted in a substantial increase in the amount of oxygen in the atmosphere. We have previously demonstrated that reaction centers from anoxygenic photosynthetic bacteria can be modified to bind a redoxactive Mn cofactor, thus gaining a key functional feature of photosystem II, which contains the site for water oxidation in cyanobacteria, algae, and plants [Thielges M, et al. (2005) Biochemistry 44:7389-7394]. In this paper, the Mn-binding reaction centers are shown to have a light-driven enzymatic function; namely, the ability to convert superoxide into molecular oxygen. This activity has a relatively high efficiency with a k cat of approximately 1 s -1 that is significantly larger than typically observed for designed enzymes, and a K m of 35-40 μM that is comparable to the value of 50 μM for Mn-superoxide dismutase, which catalyzes a similar reaction. Unlike wild-type reaction centers, the highly oxidizing reaction centers are not stable in the light unless they have a bound Mn. The stability and enzymatic ability of this type of Mn-binding reaction centers would have provided primitive phototrophs with an environmental advantage before the evolution of organisms with a more complex Mn 4Ca cluster needed to perform the multielectron reactions required to oxidize water.

Original languageEnglish (US)
Pages (from-to)2314-2318
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number7
DOIs
StatePublished - Feb 14 2012

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