Differential Analysis Of Membrane Proteins Expressed In Two Morphologic Filaments And Preliminary Study Of Actin-like Protein In Spirulina Platensis

Spirulina(Arthrospira)is a widely distributed group of prokaryote with rich protein and nutrition.As one of significant important microalgae,Spirulina produces multiplicate bioactive compounds which promote the metabolism,improve the immunity and possess unique function of health protection.In normal condition,the filament of Spirulina is regularly spiral form.However,its filaments can change from spiral to other abnormal morphologies,such as different degree of spiralization curved and even linear shapes,under intimidation of some exoteric alterative or bad environmental conditions.The specific mechanism that caused morphologies transformation of Spirulina is still unknown.To explore the morphologensis determination mechanism of Spirulina,the membrane proteins that were differentially expressed in the spiral and the linear forms from two strains Spirulina platensis FACHB 869 and FACHB 882 were respectively studied.Two dimensional gel electrophoresis was performed to separate differentially expressed proteins that were subsequently identified by MALDI-TOF mass spectrometry.The 2-DE and PMF analysis revealed that at least twelve proteins or subunits might relate to the morphogenesis of Spirulina platensis.Of these proteins, two protein spots are upwardly adjusted in linear algal trichomes,the others are downwardly adjusted in linear algal trichomes.After MALDI-TOF mass spectrographic analysis and PMF database search,10 differentially expressed proteins were identified.The identified proteins include:the translation elongation factor Ts, nitrogen metabolism associated protein,glycosyl transferase, glyceraldehyde-3-phosphate dehydrogenase,septum site-determining protein MinD, rod shape-determining protein MreB,which are related to cell wall synthesis and cytoskeleton regulation;Phycobilisomes connecting peptide CpcD,carbonate dehydratase,ferredoxin--NADP reductase,ribulose-bisphosphate carboxylase,which are participators of photosynthesis.Based on the function of cytoskeleton,prokaryotic cytoskeletal protein MreB was picked out for further research.MreB is the analogues of actin,which play a decisive role in maintaining the rod shape of bacterium.As the mreB gene sequence of Spirulina is still unknown,the mreB and actM gene from Microcystis aeruginosa PCC7806 were cloned and then expressed in E.coli.No obvious morphological changes of E.coli was observed in the over-expression experiment of fusion proteins GST-MreB or GST-ActM,which may be related to fusion proteins expression in the form of inclusion bodies.Western blot showed that MreB was slight downwardly adjusted in linear algal trichomes both in Spirulina platensis FACBH 869 and FACBH 882,which was coherent with the result from two-dimensional electrophoresis.These results indicate that MreB may be associated with the morphogenesis of Spirulina platensis.ActM's signal was not found in Spirulinal platensis.