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Kunugi M.,Hokkaido University | Takabayashi A.,Hokkaido University | Takabayashi A.,Japan Core Research for Evolutionary Science and Technology | Tanaka A.,Hokkaido University | Tanaka A.,Japan Core Research for Evolutionary Science and Technology
Journal of Biological Chemistry | Year: 2013

Chlorophyll b is found in photosynthetic prokaryotes and primary and secondary endosymbionts, although their light-harvesting systems are quite different. Chlorophyll b is synthesized from chlorophyll a by chlorophyllide a oxygenase (CAO), which is a Rieske-mononuclear iron oxygenase. Comparison of the amino acid sequences ofCAOamong photosynthetic organisms elucidated changes in the domain structures ofCAOduring evolution. However, the evolutionary relationship between the light-harvesting system and the domain structure of CAO remains unclear. To elucidate this relationship, we investigated theCAOstructure and the pigment composition of chlorophyllprotein complexes in the prasinophyte Micromonas. The Micromonas CAO is composed of two genes, MpCAO1 and MpCAO2, that possess Rieske and mononuclear iron-binding motifs, respectively. Only when both genes were introduced into the chlorophyll b-less Arabidopsis mutant (ch1-1) was chlorophyll b accumulated, indicating that cooperation between the two subunits is required to synthesize chlorophyll b. Although Micromonas has a characteristic light-harvesting system in which chlorophyll b is incorporated into the core antennas of reaction centers, chlorophyll b was also incorporated into the core antennas of reaction centers of the Arabidopsis transformants that contained the two MicromonasCAOproteins. Based on these results, we discuss the evolutionary relationship between the structures of CAO and light-harvesting systems. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.


Takahashi K.,Hokkaido University | Takabayashi A.,Hokkaido University | Takabayashi A.,Japan Core Research for Evolutionary Science and Technology | Tanaka A.,Hokkaido University | And 3 more authors.
Journal of Biological Chemistry | Year: 2014

Background: The light-harvesting complex (LHC) motif is an amino acid consensus sequence found in various thylakoid proteins. Results: Modification and replacement of the transmembrane domain encompassing the LHC motif of a plant protein retains its membrane-anchoring function but impairs its protein-protein interaction. Conclusion: This domain functions in membrane anchoring and complex formation. © 2014 by the American Society for Biochemistry and Molecular Biology, Inc. .

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