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Characterization of the peridinin-chlorophyll a-protein complex in the dinoflagellate Symbiodinium.

ABSTRACT: The water-soluble peridinin-chlorophyll a-proteins (PCPs) are one of the major light harvesting complexes in photosynthetic dinoflagellates. PCP contains the carotenoid peridinin as its primary pigment. In this study, we identified and characterized the PCP protein and the PCP gene organization in Symbiodinium sp. CS-156. The protein molecular mass is 32.7kDa, revealing that the PCP is of the monomeric form. The intronless PCP genes are organized in tandem arrays. The PCP gene cassette is composed of 1095-bp coding regions and spacers in between. Despite the heterogeneity of PCP gene tandem repeats, we identified a single form of PCP, the sequence of which exactly matches the deduced sequence of PCP gene clone 7 (JQ395030) by LC-MS/MS analysis of tryptic digested PCP, revealing the mature PCP apoprotein is 312 amino acids in length. Pigment analysis showed a peridinin-to-Chl a ratio of 4. The peridinin-to-Chl a Q(y) energy transfer efficiency is 95% in this complex.

SUBMITTER: Jiang J

PROVIDER: S-EPMC3947849 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Characterization of the peridinin-chlorophyll a-protein complex in the dinoflagellate Symbiodinium.

Jiang Jing J Zhang Hao H Kang Yisheng Y Bina David D Lo Cynthia S CS Blankenship Robert E RE

Biochimica et biophysica acta 20120404 7

The water-soluble peridinin-chlorophyll a-proteins (PCPs) are one of the major light harvesting complexes in photosynthetic dinoflagellates. PCP contains the carotenoid peridinin as its primary pigment. In this study, we identified and characterized the PCP protein and the PCP gene organization in Symbiodinium sp. CS-156. The protein molecular mass is 32.7kDa, revealing that the PCP is of the monomeric form. The intronless PCP genes are organized in tandem arrays. The PCP gene cassette is compos ...[more]

PMID: 22497797

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Project description:BackgroundThe diversity of the symbiotic dinoflagellate Symbiodinium sp., as assessed by genetic markers, is well established. To what extent this diversity is reflected on the amino acid level of functional genes such as enzymatic antioxidants that play an important role in thermal stress tolerance of the coral-Symbiodinium symbiosis is, however, unknown. Here we present a predicted structural analysis and phylogenetic characterization of the enzymatic antioxidant repertoire of the genus Symbiodinium. We also report gene expression and enzymatic activity under short-term thermal stress in Symbiodinium of the B1 genotype.ResultsBased on eight different ITS2 types, covering six clades, multiple protein isoforms for three of the four investigated antioxidants (ascorbate peroxidase [APX], catalase peroxidase [KatG], manganese superoxide dismutase [MnSOD]) are present in the genus Symbiodinium. Amino acid sequences of both SOD metalloforms (Fe/Mn), as well as KatG, exhibited a number of prokaryotic characteristics that were also supported by the protein phylogeny. In contrast to the bacterial form, KatG in Symbiodinium is characterized by extended functionally important loops and a shortened C-terminal domain. Intercladal sequence variations were found to be much higher in both peroxidases, compared to SODs. For APX, these variable residues involve binding sites for substrates and cofactors, and might therefore differentially affect the catalytic properties of this enzyme between clades. While expression of antioxidant genes was successfully measured in Symbiodinium B1, it was not possible to assess the link between gene expression and protein activity due to high variability in expression between replicates, and little response in their enzymatic activity over the three-day experimental period.ConclusionsThe genus Symbiodinium has a diverse enzymatic antioxidant repertoire that has similarities to prokaryotes, potentially as a result of horizontal gene transfer or events of secondary endosymbiosis. Different degrees of sequence evolution between SODs and peroxidases might be the result of potential selective pressure on the conserved molecular function of SODs as the first line of defence. In contrast, genetic redundancy of hydrogen peroxide scavenging enzymes might permit the observed variations in peroxidase sequences. Our data and successful measurement of antioxidant gene expression in Symbiodinium will serve as basis for further studies of coral health.

Dataset Information

Characterization of the peridinin-chlorophyll a-protein complex in the dinoflagellate Symbiodinium.

Publications

Characterization of the peridinin-chlorophyll a-protein complex in the dinoflagellate Symbiodinium.

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