Antimicrobial peptides (AMPs), named lycocitin 1, 2 and 3, and a peptide with a monoisotopic molecular mass of 3038.70 Da were detected in the venom glands of the wolf spider Lycosa singoriensis. Two of the peptides, lycocitin 1 and 2, are new AMPs whereas lycocitin 3 is highly homologous to lycotoxin II isolated from the venom of spider Lycosa carolinensis. In addition, two other peptides with monoisotopic masses of 2034.20 and 2340.28 Da showing the motif typical for antimicrobial peptides were also identified. These peptides and lycocitin 1, 2 and 3 were de novo sequenced using electron capture dissociation and low-energy collisional tandem mass spectrometry. The amino acid sequence of lycocitin 1 was determined as GKLQAFLAKMKEIAAQTL-NH(2). Lycocitin 2 differs from lycocitin 1 by a replacement of a lysine residue for an arginine residue at the second position. Lycocitin 3 differs from the known lycotoxin II consisting of 27 amino acid residues by a deletion of Gly-26. Both lycocitin 1 and 2 inhibit growth of Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria and fungi (Candida albicans, Pseudomonas aeruginosa) at micromolar concentrations.

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The structure of microcin C51, a new antibiotic prodnced by E. coli, has been determined. This antibiotic was shown to be a 1.18 kDa nucleotide peptide. It consists of a beptapeptide with formylmethionine as the N-terminus and a C-terminal asparagine linked with nebularin-5'-monophosphate through the threemethylene bridge. The OH-group of threonine is substituted. The peptide chain of microcin C51 synthesized on ribosomes is the longest among the known biologically active nucleotide peptides.Key words: Microcin; Peptide antibiotic; Nucleotide peptide and sequence were determined in an Hitachi 835 analyzer and in a Knauer Model 816 sequencer, respectively. Mass spectra were recorded using a 252Cf time-of-life plasma desorption mass-spectrometer (Experimental model, Ukraine). UV absorption spectra were recorded on a Specord M40 spectrometer (Karl Zeiss, Germany). Carbohydrate composition was determined in a Model LC200 analyzer (Biotronic, Germany) after hydrolysis in 3 M TFA at 105°C for 3 h. IH NMR spectra were taken using a Bruker spectrometer AMX-400 in D20 with acetone as an internal reference at room temperature. HMQC and 3~P/~H 2D spectra were collected on a Bruker AM-300 spectrometer using standard Bruker software [10]. Trypsin, subtilisin, and carboxypeptidases B and Y were obtained from Sigma; proteinase K was obtained from Boehringer-Mannheim.

Antimicrobial peptides (AMPs) are natural antibiotics produced by all living organisms to combat pathogens. They are important effector molecules of the immune system both in animals and plants. AMPs are diverse in structure and mode of action. Based on homology of amino acid sequences and 3D structures several AMP families have been distinguished. They are defensins, thionins, lipid transfer proteins, hevein- and knottin-like peptides, and cyclotides. AMPs display broad-spectrum antimicrobial activity and thus show promise for the development of disease- resistant crops by genetic engineering and for the production of new-generation drugs. In this paper, the properties of the main AMP families (defensins and hevein-like peptides) and of a new 4-Cys plant AMP family are reviewed.

Activated thiol-Sepharose [agarose-(glutathione-2-pyridyl disulfide) conjugate] has been used to immobilize proteins with a single or a few thiol groups via disulfide bridges. The immobilized proteins were subsequently proteolytically degraded. After washing, the thiol-containing peptides were eluted with a reducing agent. A single preparative paper electrophoresis, occasionally after a modification such as oxidation, was sufficient to obtain pure peptides in good yields. The method was applied to the major parvalbumin from hake muscle (a protein with 108 amino acid residues and one cysteine residue), to mercaptalbumin from bovine serum (565 residues and one cysteine), and to human serum ferroxidase [EC 1.16.3.1; iron (II).oxygen oxidoreductase] (ceruloplasmin) (1065 residues and three cysteines). The use of the technique, e.g., as a simple means of obtaining homologous peptides in related proteins, is discussed.