title: Nucleotide sequence of rat haptoglobin cDNA. Characterization of the alpha beta-subunit junction region of prohaptoglobin.
abstract: The biosynthesis of rat haptoglobin, a hetrotetrameric glycoprotein (alpha 2 beta 2), requires the post-translational cleavage of its glycosylated primary translation product (prohaptoglobin) into alpha- and beta-subunits (Hanley, J. M., Haugen, T. H., and Heath, E. C. (1983) J. Biol. Chem. 258, 7858-7869). To elucidate the site(s) at which proteolytic cleavage occurs in prohaptoglobin, we have isolated a recombinant plasmid whose cDNA insert encodes for the carboxyl terminus of the alpha-subunit, the alpha beta-subunit junction, and the beta-subunit region, and also the entire 3'-untranslated region (142 base pairs) and poly(A) tail (55 base pairs) of the mRNA. A single arginine residue was found at the alpha beta-subunit junction region -Val-Gln-Arg-Ile-Ile-Gly-Gly-of prohaptoglobin. The sequence homology of this region with serine protease precursors suggests that post-translational processing of prohaptoglobin involves cleavage of the Arg-Ile bond and extraction of the Arg residue. The rat beta-subunit shows a high degree (approximately 80%) of sequence homology with its human counterpart although it possesses only two of the four N-glycosylation sites present in human haptoglobin beta-subunit.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism*; D004262:DNA Restriction Enzymes; D006242:Haptoglobins / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000378:metabolism*; D046911:Macromolecular Substances; D010957:Plasmids; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000235:genetics*; D012313:RNA / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity
chemical_list: D006242:Haptoglobins; D046911:Macromolecular Substances; D011498:Protein Precursors; D012333:RNA, Messenger; C042034:prohaptoglobin; D012313:RNA; D004247:DNA; D004262:DNA Restriction Enzymes