Dynamics and orientation of amphipathic peptides in solution and bound to membranes: a steady-state and time-resolved fluorescence study of staphylococcal delta-toxin and its synthetic analogues.

The environment of both the hydrophilic and hydrophobic sides of alpha-helical delta-toxin are probed by tryptophanyl (Trp) fluorescence, when self-association occurs in solution and on binding to membranes. The fluorescence parameters of staphylococcal delta-toxin (Trp15 on the polar side of the amphipathic helix) and synthetic analogues with single Trp at position 5 or 16 (on the apolar side) were studied. The time-resolved fluorescence decays of the peptides in solution show that the local environment of their single Trp is always heterogeneous.

T cell response to myelin basic protein epitopes in multiple sclerosis patients and healthy subjects.

T cell lines and clones specific for human myelin basic protein (BP) were selected from three multiple sclerosis (MS) patients and two healthy subjects and tested for their proliferative responses to a battery of synthetic peptides, 9 to 21 amino acid residues long. The combined amino acid sequence of the peptides spanned the complete sequence of the human BP. The results suggest the development of T cells sensitized to at least four independent regions of the human BP, indicating some diversity of the human T cell repertoire to BP.

NMR and circular dichroic studies on the solution conformation of a synthetic peptide derived from the calmodulin-binding domain of Bordetella pertussis adenylate cyclase.

The solution conformation of a synthetic peptide of 20 amino acids (P235-254) derived from the calmodulin-binding domain of Bordetella pertussis adenylate cyclase was studied by proton two-dimensional NMR spectroscopy and circular dichroism. Based on the standard techniques we have assigned all the resonances in the NMR spectrum to the corresponding protons of the peptide. Analysis of the secondary chemical shift distribution and of the nuclear Overhauser effect connectivities showed no evidence for a highly populated regular conformation but suggested the tendency to form an alpha-helix around the unique Trp residue.

The amphiphilic alpha-helix concept. Consequences on the structure of staphylococcal delta-toxin in solution and bound to lipids.

Staphylococcal delta-toxin, a synthetic analogue and a fragment were studied in order to determine their structure in solution and bound in lipids. In solution, a self-association process is observed. Analytical ultracentrifuge and quasi-elastic light-scattering experiments suggest an isodesmic aggregation in the high concentration domain above 2 microM up to very large asymmetrical species.

Reaction of staphylococcal alpha-toxin with peptide-induced antibodies.

Two peptides representing separate 13-amino-acid sequences of staphylococcal alpha-toxin have been synthesized and acrylamide gel-purified alpha-toxin monomer and hexamer forms have been prepared and used to produce antisera in rabbits. We report here that each synthetic peptide, P-I and P-II, induces the formation of a specific precipitating antiserum. Moreover, these sera also react with the toxin monomer and sometimes with the hexamer, indicating that each peptide has more than one epitope.