Porin from Roseobacter denitrificans was isolated and purified to homogeneity. The pore characteristics from this marine bacterium were compared to those of its phylogenetically closely related freshwater bacteria Rhodobacter capsulatus, Rhodobacter sphaeroides and Rhodopseudomonas blastica. The porin formed weakly cation-selective, general diffusion pores in lipid bilayer membranes. High transmembrane potentials caused channel closing in steps that were of one or two thirds of the initial on-steps indicating that the porin of R. denitrificans comprised three more or less independent channels similar to PhoE and OmpC of Escherichia coli and the porin of Rhodobacter capsulatus. 37b4 Prediction of the secondary structure of the 36 N-terminal amino acid residues indicated two transmembrane beta-strands similar to those of the porins of Rhodobacter capsulatus 37b4 and Rhodopseudomonas blastica. Differences of the single channel conductivities between the porin of R. denitrificans and those of the related freshwater bacteria show that R. denitrificans evolved porin channels that are well adapted to the marine habitat.
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Article Synopsis
- The PufX protein helps certain purple bacteria with the process of exchanging two important molecules, ubiquinol and ubiquinone, in their reaction centers where they convert light into energy.
- Scientists studied this process in a type of purple bacteria called Rhodobacter capsulatus, using a special technique to see what happens when the bacteria were illuminated with light.
- They found that in bacteria without the PufX protein, the reactions weren’t as efficient, meaning that the way the molecule structure was set up made it harder for the needed molecules to reach where they needed to be in the reaction center.
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