SummaryMajor histocompatibility complex (MHC) class I molecules are cell-surface proteins that present peptides to CD8 + T cells. These peptides are mostly derived from endogenously synthesized protein. Recombinant, soluble MHC class I molecules were produced, purified, and loaded homogeneously with synthetic peptide. These MHC-peptide complexes were used to activate a T cell hybridoma. While monomers of MHC-peptide bound to the T cell, they showed no stimulatory activity. Dimers fully triggered the T cell hybridoma to secrete interleukin 2. This response was followed by a state in which the T cell was refractory to restimulation as a result of defective signal transduction through the T cell receptor.
SummaryWe investigated the role of the complementarity determining region 1 (CDR1) of T cell receptor (TCR)/3 chain both in antigen/major histocompatibility complex I (MHC I) and in superantigen (SAg)/MHC II complex recognition. Residues 26 to 31 of the VB10 domain of a TCR derived from an Hl2Ka-restricted cytotoxic clone were individually changed to alanine, using sitedirected mutagenesis, and the mutated TCR/3 chains were transfected along with the wild-type TCR c~ chain into a TCRc~-/3-T hybridoma. These mutations affected antigen/H-2K a complex recognition, although to a different extent, as estimated by interleukin 2 production. Certain mutations also affected differently the recognition of two Staphylococcal toxins, exfoliative toxin and Staphylococcal enterotoxin C2, presented by HLA-DR1. Whereas mutation of residues D30 or T31 affect the recognition of both toxins, residues T26, L27, and H29 are critical for the recognition of only one of the SAgs. These observations demonstrate the participation of the CDR1 region in the recognition of peptide/MHC class I as well as SAg/MHC II complexes.
Four overlapping cDNA clones for L‐type pyruvate kinase (PK‐L) were isolated from carbohydrate‐induced rat liver cDNA libraries. They contained all the coding sequence of the enzyme from the 7th codon and the entire 3'‐untranslated extension up to the poly(A) tail. The sequence of the first 7 codons and that of the 5'‐untranslated region were determined by primer extension. The analyzed PK‐L mRNA has 19 5'‐untranslated bases, 1629 coding bases and 1281 3'‐untranslated bases without the poly(A) tail; it corresponds to the heavier, 3.2 kb species of the L‐type mRNAs. The codons for the phosphorylatable site are, located at the 5'‐end of the messenger. The unusually long 3'‐untranslated extension contains a repetitive element complementary to the ‘brain‐specific’ identifier sequence described by Sutcliffe et al. [(1982) Proc. Natl. Acad. Sci. USA 79, 4942‐4946].
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