Site-specific mutagenesis of human interleukin-6 and its biological activity

AbstractAmino acid substitutions of human interleukin-6 (IL-6) were performed. Single substitution Met162 → Ala and double substitutions Leu159, 166 → Val resulted in a significant decrease of IL-6 activity in the production of immunoglobulin (lg) from B-cells. Single substitution Leu166→Val or Leu159→Val gave a slight or no significant decrease in the Ig-induction activity, respectively. The receptor-binding activity of each IL-6 mutant was also examined. It was observed that the decrease of the receptor-binding activity was generally in parallel with that of the Ig-induction activity. We therefore suggest that hydrophobic side-chains existing in Met162, Leu159, and Leu164 are significantly involved in the receptor-binding of IL-6

Synthesis and characterization of sapecin and sapecin B

AbstractTwo insect defencins, sapecin and sapecin B, were chemically synthesized to confirm their structure and antibacterial activity and also to examine the possibility that these peptides bind to the same site on the large conductance calcium-activated potassium channel as charybdotoxin. Both synthetic peptides showed the same antibacterial activity as native sapecins, indicating that the synthetic peptides folded correctly in the chemical synthesis. Synthetic sapecins did not show an inhibitory effect on [125I]charybdotoxin binding to rat brain synaptic membranes, suggesting that sapecin B recognizes a different binding site from that of charybdotoxin despite the similar structural motif

Characterization of mouse switch variant antibodies by matrix-assisted laser desorption ionization mass spectrometry and electrospray ionization mass spectrometry

The amino acid sequences of mouse monoclonal antibodies have been characterized completely by mass spectrometry. Antibodies used in the present study were derived from mouse switch variant cell lines that produce four kinds of immunoglobulin Gs (IgGs). The amino acid sequences of these antibodies had not been estimated from the corresponding DNA sequence, so the sequences of IgGs derived from other strains were used as references in this study. Intra- and interchain disulfide bonds of the IgGs were reduced and carboxymethylated and the products were subjected to proteolytic digestion. The existence of N-linked oligosaccharides also was taken into account. The capabilities and limitations of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and capillary liquid chromatography-electrospray ionization mass spectrometry are discussed in the structural characterization of the antibodies. Based on our results, allotypes of the antibodies examined are discussed. This study shows that amino acid sequences of proteins, such as IgG, can be investigated without information about the corresponding DNA sequence if appropriate reference sequences derived from other strains can be used

Solution dynamics in aqueous monohydric alcohol systems

The associative behavior of aqueous methanol, ethanol, and tert-butyl alcohol solutions at mole fractions ranging from 0 to 1 at 273, 283, and 298 K was examined using PGSE NMR measurements of the self-diffusion coefficients of the alkyl group, water and, depending on the exchange rate, hydroxyl protons. The results show that tert-butyl alcohol has the greatest ability to stabilize water through hydrophobic hydration than methanol or ethanol due to the more ideal fit of the tert-butyl group to the structure of water. However, at higher concentrations tert-butyl alcohol is the least able to cohesively interact with water through hydrogen bonding. The results provide compelling evidence for alcohol self-association (methanol < ethanol < tert-butyl alcohol) in very dilute solution. The alcohol molecules can be likened to very short lipid molecules undergoing complicated solution interactions due to their amphiphilic nature

Time-dependence of aggregation in crystallizing Iysozyme solutions using PGSE-NMR self diffusion measurements

The time dependence of aggregation in supersaturated lysozyme solutions was studied using pulsed-gradient spin-echo NMR diffusion measurements as a function of lysozyme concentration at pH 6.0 and 298 K in the presence of 0.5 M NaCl. The measurements provide estimates of the weight-averaged diffusion coefficient of the monomeric to intermediate molecular weight lysozyme species present in the solution (very large aggregates and crystals are excluded from the average due to the NMR relaxation-weighting effects inherent in the method). The results show that the average molecular weight of the various lysozyme aggregates changed with sigmoidal kinetics and that these kinetics were strongly influenced by the initial lysozyme concentration. The visualization of the time dependence of the protein aggregation afforded by this method provides a deeper understanding of how the crystallizing conditions (especially the initial protein concentration) are related to the resulting crystals