The porins from the halophilic species Ectothiorhodospira shaposhnikovii and Ectothiorhodospira vacuolata

Wolf, E., Zahr, M., Imhoff, Johannes F., Rosenbusch, J.P. , Schiltz, E., Zeng, J. and Weckesser, J. (1996) The porins from the halophilic species Ectothiorhodospira shaposhnikovii and Ectothiorhodospira vacuolata Archives of Microbiology, 166 . pp. 169-175. DOI 10.1007/s002030050372.

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Abstract

Major outer membrane proteins with porin activity were isolated from cell envelopes of the halophilic strains Ectothiorhodospira shaposhnikovii N1 and Ectothiorhodospira vacuolataβ1. The porins were obtained as oligomers. They dissociated into monomers by heat or EDTA treatment. The molecular masses of the monomers were determined by mass spectrometry to be 39,285 and 37,160 Da for E. shaposhnikovii N1 and E. vacuolataβ1, respectively. Both were shown by analytical ultracentrifugation to be trimers of about 112,000 Da. Circular dichroism spectra indicated predominantly β-sheet structure. The 18 N-terminal amino acid sequences of the two porins were identical except for the amino acids in positions 12 and 14. No sequence similarity with the primary structure of known porins was found. In reconstitution experiments with lipid bilayers, the porins of E. shaposhnikovii N1 and E. vacuolataβ1 formed channels with a single-channel conductance of 1.5 and 0.7 nS, respectively, in 1 M KCl. The single-channel conductance saturated with increasing salt concentration, indicating a putative binding-site for anions in the channel since both porins exhibited anion-selectivity. For the porin of E. vacuolataβ1, but not for that of E. shaposhnikovii N1, an influence of detergent concentration on the single-channel conductance was observed.

Document Type: Article
Keywords: Microbiology; Porin - Outer membrane protein - Halophilic bacteria - Ectothiorhodospira shaposhnikovii - Ectothiorhodospira vacuolata - N-terminal amino acids - Lipid bilayer studies - Anion selectivity
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-MI Marine Microbiology
Refereed: Yes
DOI etc.: 10.1007/s002030050372
ISSN: 0302-8933
Date Deposited: 18 Feb 2008 17:23
Last Modified: 26 May 2016 13:10
URI: http://eprints.uni-kiel.de/id/eprint/334

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