Spectroscopic and Molecular Characterization of the Oligomeric Antenna of the Diatom Phaeodactylum tricornutum
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- 作者：Bernard Lepetit ; Daniela Volke ; Milá ; n Szabó ; Ralf Hoffmann ; Gyö ; zö ; Garab ; Christian Wilhelm ; Reimund Goss
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：August 28, 2007
- 年：2007
- 卷：46
- 期：34
- 页码：9813 - 9822
- 全文大小：183K
- 年卷期：v.46,no.34(August 28, 2007)
- ISSN：1520-4995
文摘
The photosynthetic antenna system of diatoms contains fucoxanthin chlorophyll a/c bindingproteins (FCPs), which are membrane intrinsic proteins showing high homology to the light harvestingcomplexes (LHC) of higher plants. In the present study, we used a mild solubilization of P. tricornutumthylakoid membranes in combination with sucrose density gradient centrifugation or gelfiltration andobtained an oligomeric FCP complex (FCPo). The spectroscopic characteristics and pigment stoichiometriesof the FCPo complex were comparable to FCP complexes that were isolated after solubilization withhigher detergent per chlorophyll ratios. The excitation energy transfer between the FCP-bound pigmentswas more efficient in the oligomeric FCPo complexes, indicating that these complexes may represent thenative form of the diatom antenna system in the thylakoid membrane. Determination of the molecularmasses of the two different FCP fractions by gelfiltration revealed that the FCP complexes consisted oftrimers, whereas the FCPo complexes were either composed of six monomers or two tightly associatedtrimers. In contrast to vascular plants, stable functional monomers could not be isolated in P. tricornutum.Both types of FCP complexes showed two protein bands in SDS-gels with apparent molecular masses of18 and 19 kDa, respectively. Sequence analysis by MS/MS revealed that the 19 kDa protein correspondedto the fcpC and fcpD genes, whereas the 18 kDa band contained the protein of the fcpE gene. The presenceof an oligomeric antenna in diatoms is in line with the oligomeric organization of antenna complexes indifferent photoautotrophic groups.