Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A truncated form of the class II antigen DR alpha 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 the initiation codon was randomized so that clones with optimal expression of the truncated DR alpha chain could be obtained after induced expression and immunoscreening. The truncated DR alpha 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 the proteolytic fragments contained a disulphide bridge. It is concluded that the extracellular portion of the DR alpha chain is composed of two compactly folded domains connected by an extended stretch of the polypeptide chain.
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PMID:The extracellular portion of HLA-DR alpha chain is composed of two compactly folded domains. 365 40

The experiments in this report, together with previous studies, demonstrate that the light chains of DR antigens are composed of four domains: two large extracellular domains (each with a disulfide loop), a short hydrophobic membrane-binding region, and a short hydrophilic carboxy-terminal domain. The amino-terminal extracellular domain is glycosylated and polymorphic and has no discernible sequence homology to immunoglobulin, whereas the relatively conserved carboxy-terminal extracellular domain bears striking homology to immunoglobulin. One chymotryptic and two tryptic cleavage sites lie in the second extracellular domain of the light chain of all native DR antigens. These three sites are found in loops at the same end of an immunoglobulin-like domain. The light chain of DC1 antigen lacks one of the tryptic cleavage sites; the DR heavy chain, the class I heavy chain, and beta 2 microglobulin lack all three proteolytic sites. Proteolysis of murine la antigens with chymotrypsin and trypsin generates similar fragments (I-E-like DR, I-A-like DC1) suggesting these cleavage sites are a general feature of class II antigen light chains.
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PMID:The extracellular region of light chains from human and murine MHC class II antigens consists of two domains. 640 6