Evidence of new cadmium binding sites in recombinant horse L-chain ferritin by anomalous Fourier difference map calculation

We refined the structure of the tetragonal form of recombinant horse L-chain apoferritin to 2.0 Angstrom and we compared it with that of the cubic form previously refined to the same resolution, The major differences between the two structures concern the cadmium ions bound to the residues E130 at the threefold axes of the molecule, Taking advantage of the significant anomalous signal (f" = 3.6 e(-)) of cadmium at 1.375 Angstrom, the wavelength used here, we performed anomalous Fourier difference maps with the refined model phases. These maps reveal the positions of anomalous scatterers at different locations in the structure, Among these, some are found near residues that were known previously to bind metal ions, C48, E57, C126, D127, E130, and H132. But new cadmium binding sites are evidenced near residues E53, E56, E57, E60, and H114, which were suggested to be involved in the iron loading process. The quality of the anomalous Fourier difference map increases significantly with noncrystallographic symmetry map averaging. Such maps reveal density peaks that fit the positions of Met and Cys sulfur atoms, which are weak anomalous scatterers (f" = 0.44 e(-)). (C) 1998 Wiley-Liss, Inc

Immunocreative gonadotropin-releasing hormone-like material in the brain and the pituitary gland during the periovulatory period in the brown trout (Salmo trutta L.): Relationships with the plasma and pituitary gonadotropin

International audienceIn fish there are few data on the gonadotropin-releasing hormone (Gn-RH) neurosecretory activity, which could explain long- and short-term variations of the gonadotropin secretion. There is no biological species specificity between mammal and fish Gn-RH; although there is a structural difference, they are, on the contrary, characterized by a high immunological specificity which does not allow measurement of fish Gn-RH using radioimmunoassay for LH-RH. We have synthesized salmon Gn-RH according to the formula recently proposed by Sherwood (N. Sherwood, L. Eiden, M. Brownstein, J. Spies, J. Rivier, and W. Vale, 1983. Proc. Natl. Acad. Sci. USA 80, 2794-2798). Its activity has been tested by its ability to stimulate the gonadotropin hormone (GtH) secretion in vivo in testosterone-implanted juvenile rainbow trout, and for the recognition of synthesized Gn-RH (s-Gn-RH) perykaria by a specific antibody raised against the s-Gn-RH in regions of the brain described as containing LH-RH immunoreactive-like material. A radioimmunoassay has been developed for the salmon Gn-RH, and its specificity to measure trout Gn-RH has been tested. Using this assay, the brain and pituitary Gn-RH contents have been measured throughout the final phases of maturation and ovulation. Brain Gn-RH increases from the end of vitellogenesis (8.9 +/- 0.76 ng/brain) to ovulation (more than 15 ng/brain). Pituitary Gn-RH is lower (1.58 +/- 0.69 ng/pituitary) at the end of vitellogenesis and follows a similar profile as in the brain, except for a significant decrease just prior the beginning of oocyte maturation. The correlations between Gn-RH levels and GtH pituitary and plasma levels show that total brain Gn-RH is never correlated to the GtH, suggesting that the increase in the brain Gn-RH content is related to a Gn-RH system closely related to maturation and ovulation, which remains to be investigated. On the contrary, pituitary Gn-RH levels are well correlated with pituitary and plasma GtH levels, indicating that pituitary Gn-RH levels might represent a good index of the Gn-RH neurosecretory activity in the fish hypothalamohypophysial complex, given the absence of a portal system in teleost

Linear Oligopeptide .279. Structures of Peptides From Alpha-amino-acids Methylated At the Alpha-carbon

The structural preferences of peptides (and depsipeptides) from the achiral MeAib and Hib residues, and the chiral Iva, (alphaMe)Val, (alphaMe)Leu, and (alphaMe)Phe residues, as determined by conformational energy computations, x-ray diffraction analyses, and H-1-nmr and spectroscopic studies, are reviewed and compared with literature data on Aib-containing peptides. The results obtained indicate that helical structures are preferentially adopted by peptides rich in these alpha-amino acids methylated at the alpha-carbon. Intriguing experimental findings on the impact of the chirality of Iva, (alphaMe) Val, and (alphaMe) Phe residues on helix screw sense are illustrated