Pertussis toxin, a protein composed of five different subunits (S1, S2, S3, S4, and S5), is the major virulence factor of Bordetela pertussis. We have cloned and sequenced a DNA fragment of 4.7 kilobases that contains the genes coding for the 'five subunits. The genes are clustered within 3.2 kilobases in the following order: S1, S2, SA, S5, and S3. A sequence closely resembling Escherichia coli promoters is found only before the S1 gene, and a possible termination signal is present at the end of the S3 gene, which suggests that the pertussis toxin genes are organized in a single operon. A possible Shine-Dalgarno sequence is present before the S1 gene but not before the other four genes that 8-12 nucleotides upstream from the ATG codon show a new consensus sequence, 5'TCC(T)GG3', possibly involved in the regulation'of translation. We have also found sequence homology between the S2 and S3 genes and their protein products indicating that gene duplication played a major role in the evolution of pertussis toxin. (Fig. 2), they have a different mobility in NaDodSO4/PAGE. Note also that S5 is stained rather poorly and although its deduced molecular weight is smaller than that of S4 (Fig. 2) under reducing conditions, it migrates more slowly than S4.

In previous papers, we observed that dendrimers of peptide mimotopes of the nicotinic receptor ligand site are strong antidotes against the lethality of the nicotinic receptor ligand ␣-bungarotoxin. Although their in vitro activity is identical to that of dendrimers, the corresponding monomeric peptide mimotopes are not effective in vivo. Because the higher in vivo efficiency of dendrimers could not in this case be related to polyvalent interaction, the stability to blood protease activity of monomeric versus tetrabranched dendrimeric mimotope peptides was compared here by incubating three different mimotopes with human plasma and serum. Unmodified peptides and cleaved sequences were followed by high pressure liquid chromatography and mass spectrometry. Tetrabranched peptides were shown to be much more stable in plasma and also in serum. To assess the notable stability of multimeric peptides, different bioactive neuropeptides, including enkephalins, neurotensin and nociceptin, were synthesized in monomeric and tetrabranched forms and incubated with human plasma and serum and with rat brain membrane extracts. All the tetrabranched neuropeptides fully retained biological activity and generally showed much greater stability to blood and brain protease activity. Some tetrabranched peptides were also resistant to trypsin and chymotrypsin. Our findings provide new insights into the possible therapeutic use of bioactive peptides.Hundreds of peptides with potential therapeutic activities have been identified. These include naturally occurring peptide hormones and neurotransmitters, which influence and control series of vital functions, such as cell proliferation, tissue development, metabolism, immune defense, perception of pain, reproduction, behavior, and blood pressure. Selective agonists or antagonists of these natural peptides are extremely useful for the investigation of peptidergic systems and are also potential therapeutic agents (1). Moreover, several peptide fragments or mimotopes derived from potential therapeutic proteins show promising biological activity (2).However, the use of peptides as therapeutic drugs has largely been limited by their short half-life in vivo. Because peptides are mainly broken down by proteases and peptidases, peptide delivery is the bottleneck in the development of new peptide drugs. To increase peptide half-life, many strategies involving different levels of chemical modification are possible (3, 4). The introduction of D-amino acids, or pseudo amino acids, and peptide cyclization are the most common strategies to increase peptide stability. However, these modifications may profoundly alter peptide activity. Alternatively, peptidomimetic molecules can be developed by the synthesis of conformationally restricted compounds, in which the peptide is locally or globally constrained in order to reproduce the active conformation. The resulting structures are mostly non-peptide molecules, more resistant to degrading enzymes.In general, peptide molecules have the advantage of good specifici...

The oncofetal fibronectin (B-FN) isoform is present in vessels of neoplastic tissues during angiogenesis but not in mature vessels. B-FN could therefore provide a target for diagnostic imaging and therapy of cancer. Phage display libraries have been used to isolate human antibody fragments with pan-species recognition of this isoform. We describe the use of these fragments in nude mice to target an aggressive tumor (grafted F9 murine teratocarcinoma). Imaging in real time was done by infrared photodetection of a chemically coupled fluorophore. The targeting was improved by use of affinity-matured fragments with low kinetic dissociation rates (koff = 1.5 x 10(-4) s-1) and also by engineering dimeric fragments via a C-terminal amphipathic helix.

Peptides derived from the sequence of a single-chain, recombinant, antiidiotypic antibody (IdAb; KT-scFv) acting as a functional internal image of a microbicidal, wide-spectrum yeast killer toxin (KT) were synthesized and studied for their antimicrobial activity by using the KT-susceptible Candida albicans as model organism. A decapeptide containing the first three amino acids (SAS) of the light chain CDR1 was selected and optimized by alanine replacement of a single residue. This peptide exerted a strong candidacidal activity in vitro, with a 50% inhibitory concentration of 0.056 M, and was therefore designated killer peptide (KP). Its activity was neutralized by laminarin, a ␤1-3 glucan molecule, but not by pustulan, a ␤1-6 glucan molecule. KP also competed with the binding of a KT-like monoclonal IdAb to germinating cells of the fungus. In a rat model of vaginal candidiasis, local, postchallenge administration of KP was efficacious in rapidly abating infections caused by fluconazole-susceptible or -resistant C. albicans strains. In systemic infection of BALB/c or SCID mice preinfected intravenously with a lethal fungal load, KP caused a highly significant prolongation of the median survival time, with >80% of the animals still surviving after >60 days, whereas >90% of control mice died within 3 to 5 days. KP is therefore the first engineered peptide derived from a recombinant IdAb retaining KT microbicidal activity, probably through the interaction with the ␤-glucan KT receptor on target microbial cells.

A large 10-mer phage peptide library was panned against whole Escherichia coli cells, and an antimicrobial peptide (QEKIRVRLSA) was selected. The peptide was synthesized in monomeric and dendrimeric tetrabranched form (multiple antigen peptide [MAP]), which generally allows a dramatic increase of peptide stability to peptidases and proteases. The antibacterial activity of the dendrimeric peptide against E. coli was much higher than that of the monomeric form. Modification of the original sequence, by residue substitution or sequence shortening, produced three different MAPs, M4 (QAKIRVRLSA), M5 (KIRVRLSA), and M6 (QKKIRVRLSA) with enhanced stability to natural degradation and antimicrobial activity against a large panel of gram-negative bacteria. The MICs of the most potent peptide, M6, were as low as 4 to 8 g/ml against recent clinical isolates of multidrug-resistant Pseudomonas aeruginosa and members of the Enterobacteriaceae. The same dendrimeric peptides showed high stability to blood proteases, low hemolytic activity, and low cytotoxic effects on eukaryotic cells, making them promising candidates for the development of new antibacterial drugs.