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The Extracellular Portion of HLA‐DR α Chain is Composed of Two Compactly Folded Domains
Author(s) -
BILL P.,
LIND P.,
RASK L.,
PETERSON P. A.
Publication year - 1987
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.1365-3083.1987.tb02259.x
Subject(s) - complementary dna , start codon , microbiology and biotechnology , stop codon , signal peptide , biology , terminator (solar) , gel electrophoresis , exon , polypeptide chain , chain (unit) , chemistry , peptide sequence , genetics , messenger rna , amino acid , gene , ionosphere , physics , astronomy
A truncated form of the class II antigen DR α chain of the human major histocompatibility complex was produced in bacteria. A cDNA clone encoding the intact chain was modified so that the segment encoding the signal sequence was replaced by an ATG codon and the 3’region downstream to the part corresponding to the third exon was replaced by a stop codon. The new construct was put under the control of the Tac promoter in a bacterial expression vector. The distance between the Shine‐Delgarno sequence and Ihe initialion codon was randomized so that clones with optimal expression of the truncated DR α chain could be obtained after induced expression and immunoscreening. The truncated DR α chain was subjected to limited proteolysis with chymotrypsin. and the resulting cleavage products were analysed by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis. Two fragments were visualized by western blotting. Electrophoresis in the absence and presence of reducing agents suggested that one of Ihe proteolytic fragments contained a disulphide bridge. It is concluded that the extracellular portion of ihe DR α chain is composed of two compactly folded domains connected by an extended stretch of the polypeptide chain.