Structure and atomic fluctuation patterns of potato carboxypeptidase a inhibitor protein

Molecular dynamics (MD) simulation methods were applied to the study of the structural and dynamic fluctuation properties of the potato carboxypeptidase A inhibitor protein (PCI) immersed in a bath of 1259 water molecules. A trajectory of 200 ps was generated at constant temperature and pressure. The crystallographic structure of PCI, as found in its complex with bovine carboxy-peptidase A (CPA), was used to seed the MD simulation. Analyses show that the structure of the PCI core is fairly rigid and stable in itself, and that little deformation is caused by the protein-protein interactions found in the PCI-CPA complex. The N-terminal tail fluctuates to approach the core structure and appears as a relatively disordered region. In contrast, the conformations of the C-terminal tail, which is involved in the inhibitory mechanism, fluctuates in the neighborhood of the X-ray structure in orientations which facilitate CPA binding. Comparison with the structural entries for PCI in water obtained from both 2D-NMR experiments and X-ray data shows that important features of the MD structural results fluctuates between the initial crystal values and those obtained from the NMR solution structure. This fluctuation is not uniform; minor regions move away from the X-ray conformation while they do not approach the NMR conformation. The results reported suggest that the trajectory is long enough to show a behavior that is consistent with the conformational space available to the protein in solution.Abbreviations CPA Carboxypeptidase - DG Distance Geometry - NMR Nuclear Magnetic Resonance - NIS Non Inertial Solvent - MD Molecular Dynamics - PBC Periodic Boundary Conditions - PCI Potato Carboxypeptidase Inhibitor - RMSD Root Mean Square Deviation - a.m.u. Atomic mass units Correspondence to: O. Tapia     

Acquisition of thermotolerance in sea urchin embryos correlates with the synthesis and age of the heat shock proteins

Preheating at 31 degrees C induces thermotolerance in Paracentrotus lividus embryos, which therefore become able to withstand 1-h treatment at the otherwise lethal temperature of 35 degrees C, and to develop normally. The acquisition of thermotolerance is positively correlated with the amount of heat shock proteins produced during the 31 degrees C treatment. Evidence is provided that the heat shock proteins, although present in the embryo for long periods after synthesis, lose their effect on thermotolerance within 3 h of the cessation of synthesis.     

Evaluation of the phytosanitary, fermentative and nutritive characteristics of the silage made from crude artichoke (Cynara scolymus L.) by-product feeding for ruminants

The crude by-product left after industrial processing of artichoke (Cynara scolymus L.) was ensiled in microsilos and sampled at different times. To evaluate its suitability as animal feed, various fermentative, chemical and phytosanitary parameters were determined. The by-product showed a good aptitude for ensilage, having a pleasant smell and good visual characteristics. The DM content was 297 g kg⁻¹, and no effluents were detected. It stabilized after 12 days of ensiling and showed a pH value of 4.1 at the end of the process. Only small losses were detected in its chemical value after the ensiling period. Prometryn was the only phytosanitary product found at day 0 (0.04 ppm a concentration below the maximum amount permitted by law), but was not detected after 12 days of ensilage. It is concluded that the silage by-product can be used as animal feed.