Helper Response to Experimentally Manipulated Predation Risk in the Cooperatively Breeding Cichlid Neolamprologus pulcher

Background We manipulated predation risk in a field experiment with the cooperatively breeding cichlid Neolamprologus pulcher by releasing no predator, a medium- or a large-sized fish predator inside underwater cages enclosing two to three natural groups. We assessed whether helpers changed their helping behaviour, and whether within-group conflict changed, depending on these treatments, testing three hypotheses: ‘pay-to-stay’ PS, ‘risk avoidance’ RA, or (future) reproductive benefits RB. We also assessed whether helper food intake was reduced under risk, because this might reduce investments in other behaviours to save energy. Methodology/Principal Findings Medium and large helpers fed less under predation risk. Despite this effect helpers invested more in territory defence, but not territory maintenance, under the risk of predation (supporting PS). Experimentally covering only the breeding shelter with sand induced more helper digging under predation risk compared to the control treatment (supporting PS). Aggression towards the introduced predator did not differ between the two predator treatments and increased with group member size and group size (supporting PS and RA). Large helpers increased their help ratio (helping effort/breeder aggression received, ‘punishment’ by the dominant pair in the group) in the predation treatments compared to the control treatment, suggesting they were more willing to PS. Medium helpers did not show such effects. Large helpers also showed a higher submission ratio (submission/ breeder aggression received) in all treatments, compared to the medium helpers (supporting PS). Conclusions/Significance We conclude that predation risk reduces helper food intake, but despite this effect, helpers were more willing to support the breeders, supporting PS. Effects of breeder punishment suggests that PS might be more important for large compared to the medium helpers. Evidence for RA was also detected. Finally, the results were inconsistent with RB

The configuration of the Cu2+ binding region in full-length human prion protein compared with the isolated octapeptide

International audienc

The configuration of the Cu2+ binding region in full-length human prion protein

The cellular prion protein (PrPC) is a Cu2+ binding protein connected to the outer cell membrane. The mol. features of the Cu2+ binding sites have been investigated and characterized by spectroscopic expts. on PrPC-derived peptides and the recombinant human full-length PrPC (hPrP-[23-231]). The hPrP-[23-231] was loaded with 63Cu under slightly acidic (pH 6.0) or neutral conditions. The PrPC/Cu2+-complexes were investigated by extended X-ray absorption fine structure (EXAFS), ESR (EPR), and electron nuclear double resonance (ENDOR). For comparison, peptides from the copper-binding octarepeat domain were investigated in different environments. Mol. mechanics computations were used to select sterically possible peptide/Cu2+ structures. The simulated EPR, ENDOR, and EXAFS spectra of these structures were compared with our exptl. data. For a stoichiometry of two octarepeats per copper the resulting model has a square planar four nitrogen Cu2+ coordination. Two nitrogens belong to imidazole rings of histidine residues. Further ligands are two deprotonated backbone amide nitrogens of the adjacent glycine residues and an axial oxygen of a water mol. The authors' complex model differs significantly from those previously obtained for shorter peptides. Sequence context, buffer conditions and stoichiometry of copper show marked influence on the configuration of copper binding to PrPC

Eur Biophys J

The cellular prion protein (PrPC) is a Cu2+ binding protein connected to the outer cell membrane. The mol. features of the Cu2+ binding sites have been investigated and characterized by spectroscopic expts. on PrPC-derived peptides and the recombinant human full-length PrPC (hPrP-[23-231]). The hPrP-[23-231] was loaded with 63Cu under slightly acidic (pH 6.0) or neutral conditions. The PrPC/Cu2+-complexes were investigated by extended X-ray absorption fine structure (EXAFS), ESR (EPR), and electron nuclear double resonance (ENDOR). For comparison, peptides from the copper-binding octarepeat domain were investigated in different environments. Mol. mechanics computations were used to select sterically possible peptide/Cu2+ structures. The simulated EPR, ENDOR, and EXAFS spectra of these structures were compared with our exptl. data. For a stoichiometry of two octarepeats per copper the resulting model has a square planar four nitrogen Cu2+ coordination. Two nitrogens belong to imidazole rings of histidine residues. Further ligands are two deprotonated backbone amide nitrogens of the adjacent glycine residues and an axial oxygen of a water mol. The authors' complex model differs significantly from those previously obtained for shorter peptides. Sequence context, buffer conditions and stoichiometry of copper show marked influence on the configuration of copper binding to PrPC