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A symbiont-produced protein and bacterial symbiosis in Amoeba proteus

J W Pak1, K W Jeon

  • 1Department of Biochemistry, University of Tennessee, Knoxville, USA.

The Journal of Eukaryotic Microbiology
|January 22, 1998
PubMed

Insights

Symbiotic X-bacteria export a 29-kDa protein (S29x) into Amoeba proteus cytoplasm. This S29x protein enters the host nucleus, suggesting a role in regulating amoeba nuclear gene expression.

Area of Science:

  • Microbiology
  • Cell Biology
  • Molecular Biology

Background:

  • Gram-negative symbiotic X-bacteria reside within the xD strain of Amoeba proteus.
  • These bacteria are essential for the host cell and produce a significant amount of a 29-kDa protein, termed S29x.
  • S29x is exported from the bacteria into the host's cytoplasm, crossing both bacterial and symbiosome membranes.

Purpose of the Study:

  • To investigate the localization and potential function of the S29x protein within the host cell.
  • To understand the mechanism of S29x transport and its implications for host-symbiont interactions.

Main Methods:

  • Confocal and immunoelectron microscopy were used to detect S29x localization within Amoeba proteus.
  • The amino-acid sequence of S29x was analyzed for potential functional motifs.
  • S29x was expressed in E. coli to study its secretion properties.

Main Results:

  • S29x is efficiently secreted by X-bacteria into the host cytoplasm.
  • S29x is translocated into the nucleus of Amoeba proteus.
  • The S29x protein sequence contains a potential nuclear localization signal, and its transport is energy-independent.
  • S29x is also secreted into the culture medium when produced by genetically modified E. coli.

Conclusions:

  • The S29x protein, exported by symbiotic X-bacteria, actively enters the nucleus of its host, Amoeba proteus.
  • While its precise function remains unknown, the nuclear localization suggests S29x may influence the expression of the host's nuclear genes.
  • Further research is needed to elucidate the specific roles of S29x in the amoeba-bacteria symbiotic relationship.

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