Intracellular coupling of the heavy chain of pre-alpha-inhibitor to chondroitin sulfate.
Pre-alpha-inhibitor is a serum protein consisting of two polypeptides, the heavy chain and bikunin, covalently linked through an ester bond between the chondroitin sulfate chain of bikunin and the alpha-carboxyl group of the carboxyl-terminal residue of the heavy chain. The heavy chain is synthesized with a carboxyl-terminal extension, which is cleaved off just before the link to bikunin is formed. Our earlier studies indicate that this extension mediates the cleavage, and we have now found that a short segment on the amino-terminal side of the cleavage site is also required for the reaction. Furthermore, we previously showed that coexpression of the heavy chain precursor and bikunin in COS-1 cells leads to linkage, and we have now used this system to identify a His residue in the carboxyl-terminal extension that is specifically required for the intracellular coupling of the two proteins. In addition, we have shown that another chondroitin sulfate-containing protein, decorin, will also form a complex with the heavy chain, as will free chondroitin sulfate chains. These results suggest that in vivo there might be other, as yet unknown, chondroitin sulfate-containing polypeptides linked to the heavy chain.
Kaczmarczyk
Aneta
A
Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Center, S-751 23, Uppsala, Sweden. Aneta.Kaczmarczyk@imbim.uu.se
Thuveson
Maria
M
Fries
Erik
E
D000510:Alpha-Globulins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002809:Chondroitin Sulfates / Q000737:chemistry*; D002810:Chondroitinases and Chondroitin Lyases / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D058575:Decorin; D016326:Extracellular Matrix Proteins; D005822:Genetic Vectors; D005998:Glycine / Q000737:chemistry; D022781:Hepatocytes / Q000378:metabolism; D006639:Histidine / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D011498:Protein Precursors / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000378:metabolism; D051381:Rats; D014162:Transfection; D014360:Trypsin Inhibitor, Kunitz Soybean; D014361:Trypsin Inhibitors / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism
D000510:Alpha-Globulins; C546878:DCN protein, human; D018076:DNA, Complementary; C546879:Dcn protein, mouse; D058575:Decorin; D016326:Extracellular Matrix Proteins; D008562:Membrane Glycoproteins; D011498:Protein Precursors; D011509:Proteoglycans; C109148:SPINT2 protein, human; D014361:Trypsin Inhibitors; C016001:alpha-1-microglobulin; C061151:pre-alpha-trypsin inhibitor; D006639:Histidine; D002809:Chondroitin Sulfates; D014360:Trypsin Inhibitor, Kunitz Soybean; D002810:Chondroitinases and Chondroitin Lyases; D005998:Glycine