| Summary: | 碩士 === 國立東華大學 === 海洋生物科技研究所 === 96 === The symbiotic dinoflagellae (Symbiosdium spp) is also called zooxanthellae, which can harbore in cnidarian endoderm cell and maintain the endosymbiotic relationship. The host cell provides some nutrient and habitate for zooxanthellae, and the feedback of zooxanthellae are photosynthase supply to host. The cnidarian cells can specifically recognize the ligand (glycoprotein) on the surface of zooxanthellae, and engulf zooxanthellae into cell via receptor-mediated endocytosis (phagocytosis), and form the symbiosome as the organelle-like structure in host cytoplasm. Each zooxanthellae is bound with a membrane (called symbiosome membrane). These symbiosome membrane undoubtedly acts as an interface between cnidarian cytoplasm and zooxanthellae. Through this interface, the interaction between host and zooxanthellae was delicatedly controlled. In this study, we devoted to identify the symbiosome membrane surface proteins and reveal the molecular interaction of cnidarian-zooxanthellae endosymbiosis.
We had successfully purified the symbiosome by differential centrifugation, filtration and Percoll discontinuous gradient centrifugation. The surface proteins of purified symbiosome were tagged by biotin-XX, sulfosuccinimidly ester and then subjected to 2D electrophoresis. The biotin-tagged proteins were detected and eluted from the gel, then digested with trypsin, and finally identified by LC-nano-ESI-MS/MS.
The identified proteins were categorized as heat shock proteins (HSPs), cytoskeleton, transporter proteins and uncategorized proteins. With the known function of these proteins, we conjectured that the cytoskeleton proteins may possiblely to stabilize and maintain symbiosome properly in the host cell. The heat shock proteins may responsible for repairing and maintaining the symbiosome surface proteins that suffered the impact of free radical arising from photosynthesis. Two of the uncategoried proteins, type A GABA receptor and glial fibrillary acidic protein were also identified, both are knowen highly expressed in neuron cell. It needs to analyze the function of these two proteins on the symbiosome membrane. This pilot study reveals the nature of the symbiosome surface proteins and also provides the preliminary data to explore the molecular mechanism of cnidarian-dinoflagellat endosymbiosis.
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