Ejectisins: tough and tiny polypeptides are a major component of cryptophycean ejectisomes |
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Authors: | Silke Ammermann Tristan Schneider Martin Westermann Helmut Hillebrand Erhard Rhiel |
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Institution: | 1. Planktologie, ICBM, Carl-von-Ossietzky-Universit?t Oldenburg, P.O.B. 2503, 26129, Oldenburg, Germany 2. Elektronenmikroskopisches Zentrum am Klinikum der Friedrich-Schiller-Universit?t Jena, Ziegelmühlenweg 1, 07743, Jena, Germany
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Abstract: | Fragments of discharged ejectisomes were isolated from two Cryptomonas and a Chroomonas species by detergent treatment followed by Percoll density gradient centrifugation. The fragments withstand high concentrated detergent solutions, reducing agents and freeze-thawing. Disintegration was achieved in 6 M guanidine hydrochloride. Reassembly into long, filamentous, ejectisome-like structures occurred after dialysis. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the polypeptide patterns of isolated ejectisome fragments and of reconstituted ejectisome-like structures were dominated by polypeptides with relative molecular weights of approximately 6 kDa. The polypeptides were not glycosylated and did not cross-react with antisera directed against recombinant Reb polypeptides which constitute the R-bodies of Caedibacter taeniospiralis. A polyclonal antiserum directed against reconstituted, ejectisome-like filaments cross-reacted with the 6-kDa polypeptides and immunolabeled extruded ejectisome filaments. Twenty amino acid residues, obtained by N-terminal amino acid sequence analysis, matched to polypeptide sequences deduced from cDNA sequences of the cryptophyte Guillardia theta. The term “ejectisins” is introduced for the 6-kDa polypeptides which represent a major component of cryptophycean ejectisomes. |
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