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Journal of Bacteriology, May 2006, p. 3337-3344, Vol. 188, No. 9
0021-9193/06/$08.00+0     doi:10.1128/JB.188.9.3337-3344.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Sll0254 (CrtLdiox) Is a Bifunctional Lycopene Cyclase/Dioxygenase in Cyanobacteria Producing Myxoxanthophyll

Hatem E. Mohamed and Wim F. J. Vermaas*

School of Life Sciences, Arizona State University, P.O. Box 874501, Tempe, Arizona 85287-4501

Received 2 January 2006/ Accepted 15 February 2006

Upon depletion of Sll0254 in Synechocystis sp. strain PCC 6803, cyclized carotenoids were replaced by linear, relatively hydrophilic carotenoids, and the amount of the two photosystems decreased greatly. Full segregants of the sll0254 deletion in Synechocystis were not obtained, implying that this gene is essential for survival, most likely to allow normal cell division. The N-terminal half of Sll0254 has limited similarity to the family of lycopene cyclases, has an additional dehydrogenase motif near the N terminus, and is followed by a Rieske 2Fe-2S center sequence signature. To test whether Sll0254 serves as a lycopene cyclase in Synechocystis, the corresponding gene was expressed in Escherichia coli strains that can produce lycopene or neurosporene. In the presence of Sll0254 these linear carotenoids were converted into cyclized, relatively hydrophilic pigments, with masses consistent with the introduction of two hydroxyl groups and with spectra indicative of only small changes in the number of conjugated double bonds. This suggests that Sll0254 catalyzes formation of oxygenated, cyclized carotenoids. We interpret the appearance of the hydroxyl groups in the carotenoids to be due to dioxygenase activity involving the Rieske 2Fe-2S center and the additional dehydrogenase domain. This dioxygenase activity is required in the myxoxanthophyll biosynthesis pathway, after or concomitant with cyclization on the other end of the molecule. We interpret Sll0254 to be a dual-function enzyme with both lycopene cyclase and dioxygenase activity and have named it CrtLdiox.

* Corresponding author. Mailing address: School of Life Sciences, Arizona State University, P.O. Box 874501, Tempe, Arizona 85287-4501. Phone: (480) 965-6250. Fax: (480) 965-6899. E-mail: wim{at}asu.edu.

Journal of Bacteriology, May 2006, p. 3337-3344, Vol. 188, No. 9
0021-9193/06/$08.00+0     doi:10.1128/JB.188.9.3337-3344.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Graham, J. E., Bryant, D. A. (2009). The Biosynthetic Pathway for Myxol-2' Fucoside (Myxoxanthophyll) in the Cyanobacterium Synechococcus sp. Strain PCC 7002. J. Bacteriol. 191: 3292-3300 [Abstract] [Full Text]  
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