title: Evidence of functional trimeric chlorophyll a/c2-peridinin proteins in the dinoflagellate Symbiodinium.
abstract: The chlorophyll a-chlorophyll c2-peridinin-protein (apcPC), a major light harvesting component in peridinin-containing dinoflagellates, is an integral membrane protein complex. We isolated functional acpPC from the dinoflagellate Symbiodinium. Both SDS-PAGE and electrospray ionization mass spectrometry (ESI-MS) analysis quantified the denatured subunit polypeptide molecular weight (MW) as 18kDa. Size-exclusion chromatography (SEC) and blue native gel electrophoresis (BN-PAGE) were employed to estimate the size of native acpPC complex to be 64-66kDa. We also performed native ESI-MS, which can volatilize and ionize active biological samples in their native states. Our result demonstrated that the native acpPC complex carried 14 to 16 positive charges, and the MW of acpPC with all the associated pigments was found to be 66.5kDa. Based on these data and the pigment stoichiometry, we propose that the functional light harvesting state of acpPC is a trimer. Our bioinformatic analysis indicated that Symbiodinium acpPC shares high similarity to diatom fucoxanthin Chl a/c binding protein (FCP), which tends to form a trimer. Additionally, acpPC protein sequence variation was confirmed by de novo protein sequencing. Its sequence heterogeneity is also discussed in the context of Symbiodinium eco-physiological adaptations.
authors.affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Orf
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Wenxin
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Lucas B
authors.initials: LB
authors.lastname: Harrington
authors.affiliation: Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Haijun
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Cynthia S
authors.initials: CS
authors.lastname: Lo
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA; Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA. Electronic address: blankenship@wustl.edu.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
keywords: Chlorophyll a/c(2)-peridinin-protein; Light-harvesting complex; Native mass spectrometry; Symbiodinium