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Thermodynamic Stability of Psychrophilic and Mesophilic Pheromones of the Protozoan Ciliate Euplotes

“…This finding coincides with observations derived from comparisons between other psychrophilic and mesophilic homologous proteins [29,30,31,32,33]. However, while these comparisons are essentially based on individual proteins from distantly related organisms, our finding involves families of proteins with known NMR solution structures [11,12,13,14,15,16,17,18,19,20,21] from two closely related species [34,35]. It therefore provides data which, at least in principle, are more reliable (being unaffected by the evolutionary noise which is intrinsic to comparisons between distantly related systems) for further detailed analyses by other groups of researchers who are interested in studying the correlations between protein structure, thermodynamic stability, and cold-adaptation.…”

“…These water-borne “pheromones” are functionally associated with the genetic mechanism of the mating types and act as prototypic autocrine (autologous) growth factors and as paracrine (heterologous) inducers of mating pair formation [6,7]. In addition to the full-length coding gene sequences [8,9,10], the three-dimensional molecular structures of a significant number of pheromones were determined by NMR spectroscopy in solution, firstly, from the temperate-water species, E. raikovi [11,12,13,14,15,16,17], and subsequently from the polar-water species, E. nobilii [18,19,20]. These mesophilic ( E. raikovi ) and psychrophilic ( E. nobilii ) pheromone families, both characterized by small, helical and disulfide-rich proteins of 37 to 63 amino acids, thus represent an interesting source of material for structure based comparative studies of protein adaptation to cold.…”

Structural characterization of a protein pheromone from a cold‐adapted (Antarctic) single‐cell eukaryote, the ciliate Euplotes nobilii

“…However, similar predictions for E. raikovi pheromones have been disproved by results from crystallographic and nuclear magnetic resonance analyses [15,17]. Not only have these analyses established that the structure of these molecules exclusively consists of a bundle of three α‐helices tightly associated by three disulfide bonds [6,14–16], or (limitedly to the case of pheromone E r ‐23) of a bundle of five helices interconnected by five disulfide bonds [17]; but they have also provided evidence that a key role in enforcing and stabilizing these configurations is played by the high density and strategic disposition of the disulfide bonds [17]. The fact that six of the eight E n ‐2 cysteines find their precise counterparts in the ‘standard’ six cysteines of E. raikovi pheromones (Fig.…”

“…Multiple sequence alignment between E n ‐2 and the E. raikovi pheromones was based on the CLUSTAL algorithm [25]. Only E. raikovi pheromones with six cysteines and a known three‐dimensional structure have been considered [6,14–16]. Cysteine residues (printed in bold) located in conserved positions between E n ‐2 and E. raikovi pheromones are marked by asterisks and paired by lines to denote the disulfide arrangement originally determined in E. raikovi pheromones E r ‐1 and E r ‐2 [26].…”

Ciliate pheromone structures and activity: a review

“…Notwithstanding this wide amino acid sequence variability, the determination of the three-dimensional architectures of pheromones Er-1, Er-2, Er-10, Er-11, Er-22 and Er-23 by NMR spectroscopy and (limited to Er-1) X-ray crystallography has shown that these molecules all share a common structural folding ( Figure 2B). This is provided by a complex of three right-handed α helices (five in Er-23, of which the additional two are very short and single-turn helices), which take a a nearly parallel and up-down-up orientation (Brown et al 1993;Luginbühl et al 1994;Mronga et al 1994;Ottiger et al 1994;Weiss et al 1995;Liu et al 2001;Zahn et al 2001). The three helices are linked together by closely spaced and tightly conserved disulfide bonds, two of which involve potential alternative cysteine pairings that have been found to be consistent with major NMR constraints and the formation of native disulfide isomers (Brown et al 1993).…”