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Channel forming outer membrane porin protein in halophile: expressed as a soluble form in Escherichia coli

Hiroko Tokunaga1, Masafumi Furukawa, Tsutomu Arakawa

  • 1Applied and Molecular Microbiology, Faculty of Agriculture, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.

International Journal of Biological Macromolecules
|December 11, 2012
PubMed

Insights

Researchers cloned the halophilic outer membrane protein P (hopP) gene from Halomonas sp. 40. This porin protein exhibits permeability and forms a beta-sheet structure in response to salt, crucial for halophilic bacteria.

Area of Science:

  • Microbiology
  • Structural Biology
  • Biochemistry

Background:

  • Outer membrane proteins in Gram-negative bacteria often form pores.
  • Moderate halophiles, like Halomonas sp. 40, possess unique outer membrane proteins.
  • Previous work identified a porin-like protein in Halomonas sp. 40.

Purpose of the Study:

  • To clone and characterize the gene encoding a major outer membrane protein from Halomonas sp. 40.
  • To investigate the structural and functional properties of the identified halophilic outer membrane protein (hopP).

Main Methods:

  • Gene cloning based on N-terminal and internal amino acid sequences.
  • Protein expression in Escherichia coli with N-terminal His-tag.
  • Liposome reconstitution and permeability assays.
  • Circular dichroism spectroscopy.

Main Results:

  • The halophilic outer membrane protein P (hopP) gene was successfully cloned from Halomonas sp. 40.
  • The encoded porin precursor contains a signal peptide; the mature protein is acidic and soluble.
  • Recombinant His-porin retained solubility after heat treatment and showed salt-dependent beta-sheet formation.

Conclusions:

  • The cloned hopP gene encodes a functional porin from a moderate halophile.
  • The protein's structural properties, particularly its beta-sheet formation in response to salt, are significant for its function in a high-salt environment.

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