C-terminal post-translational proteolysis of plant lectins and their recombinant forms expressed in Escherichia coli. Characterization of "ragged ends" by mass spectrometry.

Electrospray mass spectrometry was used to accurately measure the molecular masses of single chain lectins from legume seeds and also of three recombinant lectins, expressed in Escherichia coli. The five single chain lectins, Erythrina corallodendron lectin, soybean and peanut agglutinins, Dolichos biflorus lectin, and Phaseolus vulgaris hemagglutinin E, all showed evidence of C-terminal proteolytic processing, in some cases to "ragged" ends, when their masses were compared to those expected from their cDNA sequences and their known carbohydrate chains. Recombinant forms of the lectins from E. corallodendron, soybean, and peanut also showed C-terminal trimming, but not to the same points as the natural forms. Discrepancies between the protein and cDNA sequences of the E. corallodendron lectin were resolved by combined liquid chromatography-mass spectrometry peptide mapping and protein sequencing experiments, and the presence of a second glycosylation site was demonstrated. Our data show that all of these lectins undergo C-terminal proteolytic processing of a readily attacked peptide segment. This trimming is frequently imprecise, and the resulting heterogeneity may be a major contributor to the appearance of isolectin forms of these proteins.

The lack of effect of inoculation with equine influenza vaccine on theophylline pharmacokinetics in the horse.

Several studies conducted during the past few years have shown that the pharmacokinetics of a variety of drugs may be altered following viral infection or vaccination. The elimination of drugs which are extensively metabolized, such as theophylline, may be prolonged, especially following exposure to RNA viruses such as Type A influenza or similar orthomyxoviruses. The purpose of this study was to determine whether vaccination of horses with equine influenza virus affected pharmacokinetic parameters describing the distribution and elimination of intravenously administered theophylline. Three thoroughbred horses and three ponies were vaccinated with a trivalent vaccine containing inactivated strains of A/Equi 1 (Prague), A/Equi 2 (Miami) and A/Equi 2 (Kentucky 81). Antibody titre, serum interferon concentrations, and the pharmacokinetic parameters t1/2 beta, Vc, Vd(ss), Vd(area) and ClB were measured at various intervals after vaccination. Antibody titre increased substantially in only two animals, while plasma interferon was detectable in low concentrations in four subjects. There was no significant change in any parameter describing the pharmacokinetics of theophylline when measured 2, 6, or 12 days after vaccination. It is suggested that the failure of vaccination to substantially increase plasma interferon concentrations, and thereby alter theophylline elimination, was related to the use of an inactivated viral vaccine, the only type available for vaccination of horses against infection with equine influenza. Regular use of such vaccines, as is required by most Racing Authorities, is therefore unlikely to affect drug withdrawal times.