Conformation of the transmembrane domains in peripheral myelin protein 22. Part 1. Solution-phase synthesis and circular dichroism study of protected 17-residue partial peptides in the first putative transmembrane domain

Charcot-Marie-Tooth disease (CMT) is the most commonly inherited peripheral neuropathy. DNA duplication and point mutation of the gene encoding peripheral myelin protein 22 (PMP22) have been found in CMT type 1A dominants. To investigate the influence of the point mutation of PMP22 on the secondary structure, protected partial peptides in the putative first transmembrane domain, wild type Boc-IVLH(Bom)VAVLVLLFVSTIV-OMe (1) and its Pro16 mutant Boc-IVLH(Bom)VAVPVLLFVSTIV-OMe (2) were synthesized. Circular dichorism (CD)-spectral analysis suggested that peptide 1 adopts a stable alpha-helical conformation in membrane-mimetic solvent,1-BuOH/1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) system. On the contrary, the mutant 2 favors beta-sheet conformation in the same solvent system. Interestingly, alpha-helix to beta-sheet transition of 2 was observed at higher contents of 1-BuOH than 70%.

Multiple peptide synthesis on polypropylene membranes for rapid screening of bioactive peptides

A new multiple peptide synthesis technique that allows several hundred peptides to be synthesized on polypropylene membranes in one working day has been developed. Peptides are assembled as spots on a membrane sheet sandwiched between two 96-reaction well templates. Activity measurements can be made either with the membrane-bound peptides, for example, using an enzyme linked immunosorbent assay (ELISA), or after cleavage from the membrane. The method is simple and economical in the use of reagents, and peptides are of high quality, making possible the synthesis of rather long (> 20 residues) peptides. This method has been used to identify antigenic determinants recognized by antisera to bovine myelin proteolipid protein.

Identification of an encephalitogenic determinant of myelin proteolipid protein for SJL mice

PLP is the major protein constituent of central nervous system myelin. We have previously shown that SJL/J (H-2s) mice develop an acute form of EAE after immunization with PLP. The purpose of the present study was to identify an encephalitogenic determinant of PLP for SJL mice. We immunized SJL/J mice with a synthetic peptide identical to residues 130-147 QAHSLERVCHCLGKWLGH of murine PLP, a sequence having an amphipathic alpha-helical conformation. Although it did not induce disease, an overlapping peptide containing residues 139-154 HCLGKWLGHPDKFVGI was encephalitogenic. Immunization with this peptide induced severe clinical and histologic EAE in 3 of 20 mice. T cell enriched ILN cells from these mice responded specifically (3H-thymidine incorporation) to this peptide as well as to shorter analogues of this domain containing serine in place of cysteine at residues 138 and 140. Immunization with the serine-substituted PLP peptides 137-151 VSHSLGKWLGHPDKF and 139-151 HSLGKWLGHPDKF induced severe, acute EAE in 4 of 9 and 15 of 15 SJL mice, respectively, and their T cell enriched ILN cells responded not only to the analogues, but also to the native PLP sequence 139-154. These results indicate that residues 139-151 of murine PLP is an encephalitogenic determinant for SJL mice. Furthermore, like the PLP encephalitogenic domain for SWR (H-2q) mice, this determinant is also a T cell epitope with a coding sequence at the end of an exon.