, Volume 182, Issue 3, pp 348–354 | Cite as

Biochemical and physiological properties of a protein inducing protoplast release during conjugation in theClosterium peracerosum-strigosum-littorale complex

  • Hiroyuki Sekimoto
  • Shinobu Satoh
  • Tadashi Fujii


When mating-type minus (mt) and plus (mt+) cells of theClosterium peracerosum-strigosum-littorale complex were mixed together in a nitrogen-deficient mating medium, cells of both types released protoplasts, this release being the first step in the process of conjugation. Release of protoplasts by mt cells also proceeded without pairing in a medium in which mt and mt+ cells had previously been cultured together. A protein with the ability to induce the release of protoplasts was purified from this medium by sequential column-chromatographic steps, and named PR-IP (protoplast-release-inducing protein). The PR-IP had an apparent molecular mass (Mr) of 95000 on gel filtration and could be separated into several isoforms by anion-exchange chromatography. Each isoform consisted of two glycopolypeptides of Mrs 42000 and 19000, while the deglycosylated polypeptides had Mrs of 34000 and 18000, respectively. From an analysis of dose-response curves, the numbers of PR-IP molecules required for the release of a protoplast by a single cell was calculated as 1.5·109 and the concentration required for 50% of the maximum response (ED50) as 4.1·10−9M. We suggest that the PR-IP is a biologically active glycoprotein which induces the release of gametic protoplasts from mt cells of thisClosterium complex.

Key words

Closterium Conjugation (ClosteriumGlycoprotein Protoplast release in conjugation 




MI medium

nitrogen-deficient mating medium


apparent molecular mass




protoplast-release-inducing protein


sodium dodecyl sulfate-polyacrylamide gel electrophoresis


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Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • Hiroyuki Sekimoto
    • 1
  • Shinobu Satoh
    • 1
  • Tadashi Fujii
    • 1
  1. 1.Institute of Biological SciencesUniversity of TsukubaTsukuba, IbarakiJapan

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