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  • 标题:Biosynthesis and self-assembly of protein S, a development-specific protein of Myxococcus xanthus
  • 本地全文:下载
  • 作者:Masayori Inouye ; Sumiko Inouye ; David R. Zusman
  • 期刊名称:Proceedings of the National Academy of Sciences
  • 印刷版ISSN:0027-8424
  • 电子版ISSN:1091-6490
  • 出版年度:1979
  • 卷号:76
  • 期号:1
  • 页码:209-213
  • DOI:10.1073/pnas.76.1.209
  • 语种:English
  • 出版社:The National Academy of Sciences of the United States of America
  • 摘要:Myxococcus xanthus is a Gram-negative bacterium that has a complex life cycle including a temporal sequence of cellular aggregation, mound formation, and myxosporulation. During development, protein S (molecuar weight 23,000) is induced and accumulates in very large amounts. Protein S was found in the soluble fraction of early developmental extracts and in the insoluble fraction in later extracts. This insoluble form of protein S can be solubilized by the addition of 1 M NaCl at 0{degrees}C to extracts from aggregated cells (mound stage) or by the addition of 1 M NaCl at 30{degrees}C to mature spores. Salt extraction (1 M NaCl) of protein S from mature spores was partially inhibited by the addition of Mg2+ and almost completely inhibited by the addition of Ca2+. The viability of spores was not changed by a salt extraction that removed their protein S. Examination of thin sections of mature spores and extracted spores by electron microscopy suggested that the protein S-deficient spores lacked a spore surface coat about 300 A thick. Purified protein S will spontaneously self-assemble onto protein S-deficient spores after removal of the NaCl by dialysis or by addition of 10 mM Ca2+ to undialyzed samples. Glycerol-induced spores did not contain protein S and did not serve as primers for assembly of protein S. Quantitation of the self-assembly process showed almost stoichiometric binding of protein S to the protein S-deficient spores until saturation at 3.3 x 106 molecules per spore, a value 1.35 times higher than the normal level of proteins S found in mature spores. Protein S in the "reconstituted" spores was as protease resistant and sonication resistant as the protein S of native spores. Electron microscopy of the reconstituted spores revealed the assembly of new material on the spore surface. Adjacent spores were sometimes observed to be fused to each other through a common protein S layer. These results suggest that protein S serves a function in spore--spore interaction in the fruiting body.
  • 关键词:spores ; fruiting body ; sodium dodecyl sulfate gel electrophoresis ; calcium ion
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