Journal Article

Oxygen Sensitivity of a Nitrogenase-like Protochlorophyllide Reductase from the Cyanobacterium <i>Leptolyngbya boryana</i>

Haruki Yamamoto, Shohei Kurumiya, Rie Ohashi and Yuichi Fujita

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 9, pages 1663-1673
Published in print September 2009 | ISSN: 0032-0781
Published online July 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp111
Oxygen Sensitivity of a Nitrogenase-like Protochlorophyllide Reductase from the Cyanobacterium Leptolyngbya boryana

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Dark-operative protochlorophyllide (Pchlide) oxido-reductase (DPOR) is a nitrogenase-like enzyme that catalyzes Pchlide reduction, the penultimate step of chlorophyll a biosynthesis. DPOR is distributed widely among oxygenic phototrophs such as cyanobacteria, green algae and gymnosperms. To determine how DPOR operates in oxygenic photosynthetic cells, we constructed two shuttle vectors for overexpression of Strep-tagged L-protein (ChlL) and Strep-tagged NB-protein (ChlN–ChlB) in Leptolyngbya boryana (formerly Plectonema boryanum) and introduced them into mutants lacking chlL and chlB. Both transformants restored the ability to produce chlorophyll in the dark. The DPOR activity was reconstituted by L-protein and NB-protein purified from the transformants under anaerobic conditions. L-protein activity disappeared within 5 min of exposure to air while NB-protein activity persisted for >30 min in an aerobic condition, indicating that the L-protein of DPOR components is the primary target of oxygen in cyanobacterial cells. These results suggested that the DPOR from an oxygenic photosynthetic organism did not acquire oxygen tolerance during evolution; but that the cyanobacterial cell developed a mechanism to protect DPOR from oxygen.

Keywords: Chlorophyll biosynthesis; Cyanobacteria; Dark-operative protochlorophyllide oxidoreductase; Leptolyn-gbya boryana; Nitrogenase-like enzyme

Journal Article.  6295 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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