RESUMO
The bis-cysteinyl hinge-fragment 225-232 of human IgG1 has been extended at the N- or C-terminus with Nle15-desamido-human-little-gastrin-[5-17] and Nle15-human-little-gastrin-[5-17]-NH2, respectively. Thermodynamically controlled air oxidation of the resulting bis-cysteinyl-peptides led to the predominant formation of the corresponding dimers in parallel alignment despite the incorporation of the immunoglobulin-unrelated gastrin-sequences. These surprising results confirm the high degree of structural information inherent in the hinge-sequence and its intrinsic tendency to fold into the correct structure in terms of cysteine pairings. This protein subdomain-the hinge-peptide-is therefore well suited as core molecule for the design of fully synthetic immunogens with multiple attachment of antigenic determinants.
Assuntos
Antígenos/síntese química , Peptídeos/síntese química , Sequência de Aminoácidos , Antígenos/química , Gastrinas/síntese química , Gastrinas/química , Gastrinas/imunologia , Humanos , Imunoglobulina G/síntese química , Imunoglobulina G/química , Dados de Sequência Molecular , Fragmentos de Peptídeos/síntese química , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/imunologia , Peptídeos/química , Peptídeos/imunologia , Conformação ProteicaRESUMO
In human IgGl the two heavy chains are crosslinked in the central portion of the molecule by two disulfide bridges forming a double chain bis-cystinyl cyclic peptide in parallel alignment. For our synthetic studies we have chosen the sequence portion 225-232/225'-232', i.e. [H-Thr-C1ys-Pro-Pro-C1ys-Pro-Ala-Pro-OH]2. By the use of a combination of the S-tert.-butylthio and the S-acetamidomethyl groups selective cysteine pairings in two successive steps produced the hinge hexadecapeptide in parallel and antiparallel alignment as homogeneous and well characterized compounds. Thiol disulfide interchange experiments on the antiparallel dimer led to over 90% conversion to the parallel isomer. Similarly random air-oxidation was found to generate again mainly the parallel dimer, thus strongly suggesting that this sequence portion contains sufficient structural information for a correct assembly of the two heavy chains of immunoglobulins without decisive contribution of a protein disulfide isomerase.
