Structural and functional analysis of water-borne signaling protein pheromones from the bipolar protist ciliate, Euplotes petzi

• Main Authors: Roberta Russo, Claudio Alimenti, Adriana Vallesi, Cinzia Verde, Bill Pedrini, Pierangelo Luporini
• Other Authors: Jana Kvíderová , Daria Tashyreva, Alexandra Bernardová, Josef Elster, Russo, Roberta, Alimenti, Claudio, Vallesi, Adriana, Verde, Cinzia, Pedrini, Bill, Luporini, Pierangelo
• Format: Conference Object
• Language: English
• Published: Faculty of Science, University of South Bohemia in České Budějovice 2015
• Subjects: Arctic; Antarctic; Antarc*
• Online Access: http://hdl.handle.net/11581/419708; http://polaralpinemicrobiology2015.prf.jcu.cz/pages/index

Polar ecosystems host a rich variety of micro-eukaryotic organisms and protozoan ciliates are a major component (1, 2). They can readily be collected from every aquatic habitat and expanded into stable laboratory cultures providing excellent experimental material for research in polar biology. Among numerous Antarctic and Arctic marine species of Euplotes that have been adapted to grow in captivity, we have focused particular interest on E. petzi: a psychrophilic species with a bipolar distribution capable of constitutively secreting signaling protein pheromones in functional association with its genetic mechanism of multiple mating types (3). Four structurally distinct E. petzi pheromones (designated Ep-1, Ep-2, Ep-3 and Ep-4) have been purified and structurally characterized from cell-free filtrates of cultures of genetically different E. petzi strains (4). They are proteins with sequences of only 32 amino acids with eight cysteines arranged in four intra-chain disulfide bridges which stabilize a molecular architecture characterized by two helices, one formed by only four residues and the other one by eight. Of the two pheromones Ep-1 and Ep-2 (that can be purified in more abundance), we have analyzed the thermal unfolding and refolding properties on the basis of circular dichroism (CD) spectra. It appears that the E. petzi pheromones Ep-1 and Ep-2 are thermally stable proteins, like the pheromones that we have comparatively analyzed from the temperate-water species E. raikovi.