Purification and Characterization of the Major Lipoprotein (P28) of Spiroplasma apis |
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Authors: | Michel Le Hnaff Jean-Yves Crmet Catherine Fontenelle |
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Institution: | a Groupe “Membranes et Osmorégulation” Campus de Beaulieu, Université de Rennes 1, UMR-CNRS 6026, F-35042, Rennes Cedex, France;b Laboratoire de Microbiologie et de Biochimie Appliquées, Ecole Nationale d'Ingénieurs des Travaux Agricoles de Bordeaux, 1, Cours du Général de Gaulle, BP 201, F-33175, Gradignan Cedex, France |
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Abstract: | The plasma membrane of Spiroplasma apis contains a 28-kDa major protein (P28), like other spiroplasmas which also possess a main 26- to 28-kDa membrane polypeptide, called spiralin. In the work described here, we have developed a simple and efficient method for the purification of P28 of this mollicute, a wall-less eubacteria. Proteins were first selectively extracted from the isolated membrane with the mild detergents (i) sodium N-lauroylsarcosinate (Sarkosyl) and (ii) 3-(3-cholamidopropyl)dimethylamonio]-1-propyl sulfonate (Chaps) and subjected to size-exclusion HPLC in the presence of Chaps. The P28-enriched fraction was thereafter subjected to the second chromatographic step involving cation exchange HPLC in the presence of the same detergent. P28 was purified at the milligram level (yield, 40%). Metabolite labeling with 14C]palmitic acid and chemical analysis of P28 indicated that it is covalently modified by two O-ester-bound fatty acids and one amide-linked chain and contains a S-glycerylcysteine at the N-terminus. By charge-shift electrophoresis, Triton X-114 phase separation, and growth inhibition tests it was shown that P28 is a typical amphiphilic protein exposed, at least partly, at the cell surface. Together, our data provided evidence that P28 is a “classical” lipoprotein (i.e., triacylated) like the members of the spiralin family. |
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Keywords: | mollicutes spiroplasma membrane proteins lipoproteins spiralin |
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