Animals and higher plants express endogenous peptide antibiotics called defensins. These small cysteine-rich peptides are active against bacteria, fungi and viruses. Here we describe plectasin-the first defensin to be isolated from a fungus, the saprophytic ascomycete Pseudoplectania nigrella. Plectasin has primary, secondary and tertiary structures that closely resemble those of defensins found in spiders, scorpions, dragonflies and mussels. Recombinant plectasin was produced at a very high, and commercially viable, yield and purity. In vitro, the recombinant peptide was especially active against Streptococcus pneumoniae, including strains resistant to conventional antibiotics. Plectasin showed extremely low toxicity in mice, and cured them of experimental peritonitis and pneumonia caused by S. pneumoniae as efficaciously as vancomycin and penicillin. These findings identify fungi as a novel source of antimicrobial defensins, and show the therapeutic potential of plectasin. They also suggest that the defensins of insects, molluscs and fungi arose from a common ancestral gene.

Background: FcRn controls the long serum half-life of albumin. Results: A single amino acid substitution of albumin considerably improved binding to FcRn and extended serum half-life in mice and rhesus monkeys. Conclusion: Serum half-life of albumin may be tailored by engineering the FcRn-albumin interaction. Significance: This study reports on engineered albumin that may be attractive for improving the serum half-life of biopharmaceuticals.

We describe a rapid, sensitive and semi-quantitative plate assay for monitoring pheromone activity in the fission yeast Schizosaccharomyces pombe. It is based on the observation that meiosis requires stimulation by pheromone and exploits diploid strains that will only sporulate after addition of exogenous pheromone. The tester strains are heterozygous for mating type, are non-switching, and are mutated in one of the early subfunctions (either mat1-Mc or mat1-Pc), so that meiosis is only induced after exposure to exogenous pheromone (M-factor or P-factor, respectively). Pheromone activity is assessed as an iodine-positive halo of sporulation surrounding the pheromone source, and the width of the halo is related to the amount of pheromone being produced. The assay is sufficiently sensitive to monitor the low amount of M-factor produced by an M mam1 strain, and its sensitivity towards P-factor is greatly increased by using a hyper-sensitive tester strain lacking the Sxa2 protease that is believed to degrade this pheromone. We also demonstrate that the production of P-factor is very much stimulated by exposure of P cells to M-factor.

We previously identified two genes, mfinl and mfin2, with the potential to encode the M-factor mating pheromone of the fission yeast Schizosaccharomyces pombe (J. Davey, EMBO J. 11:951-960, 1992), but further analysis revealed that a mutant strain lacking both genes still produced active M-factor. Here we describe the isolation and characterization of a third M-factor gene, mfm3. A mutant lacking all three genes fails to produce M-factor, indicating that all functional M-factor genes now have been identified. The triple mutant exhibits an absolute mating defect in M cells, a defect that is not rescued by addition of exogenous M-factor. A mutational analysis reveals that all three mJfm genes contribute to the production of M-factor. Their transcription is limited to M cells and requires the matl-Mc and stell gene products. Each gene is induced when the cells are starved of nitrogen and further induced by a pheromone signal. Additionally, the signal transduction machinery associated with the pheromone response is required for transcription of the mfm genes in both stimulated and unstimulated cells.The fission yeast Schizosaccharomycespombe exists in one of two mating types, minus (M) or plus (P), and under the appropriate conditions, cells of opposite mating type can conjugate to form a diploid zygote (reviewed in reference 45). Prior to conjugation, the cells communicate with each other via diffusible mating pheromones that prime the recipient cell for mating; M cells release M-factor, which prepares P cells for mating, and P cells secrete P-factor, which stimulates M cells. Pheromone-induced changes include a G1 arrest of the cell cycle (9, 26), an altered pattern of gene transcription (46), and elongation of the cell (7,19,36).The response begins when the pheromone binds to a Gprotein-coupled receptor on the surface of the target cell; receptors for P-factor are encoded by the mam2 gene (29), while those for M-factor are encoded by map3 (58). Stimulation of the receptor is thought to cause dissociation of the G protein such that the Got subunit (encoded bygpal [49]) is able to trigger an intracellular signalling pathway which includes a cascade of protein kinases encoded by the byrl, byr2, and spkl genes (42,44,56,59,61). A number of these enzymes are functionally homologous to the mitogen-activated protein kinases believed to be involved in controlling the proliferation and differentiation of mammalian cells (reviewed in reference 16). Transmission of the pheromone signal also requires the rasl gene product, the S. pombe homolog of the mammalian ras oncogene (20,46).The M-factor pheromone is a nonapeptide in which the C-terminal cysteine residue is S farnesylated and carboxyl methylated (7,8,60); P-factor is a peptide made of 23 residues and is probably unmodified (26). Although the biogenesis of M-factor is not fully characterized, it is likely to be similar to * Corresponding author. Mailing address: