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

James P. Allen, Tien L. Olson, Paul Oyala, Wei Jen Lee, Aaron A. Tufts, Jo Ann C. Williams

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

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
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
Publication statusPublished - Feb 14 2012

ASJC Scopus subject areas

  • General

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