Comparison of the binding of chicken alpha-macroglobulin and ovomacroglobulin to the mammalian alpha 2-macroglobulin receptor.
Chicken alpha-macroglobulin (alpha M) and ovomacroglobulin were purified by Ni+2 chelate chromatography. These proteins had similar subunit structure as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Chicken alpha M bound 1.0 mol and ovomacroglobulin bound 0.8 mol 125I-trypsin per mol inhibitor, respectively. Ovomacroglobulin cleared rapidly from the circulation of mice, and the clearance was inhibited by asialoorosomucoid, but native chicken alpha M cleared slowly (t 1/2 greater than 1 h). After reaction with trypsin, this alpha-macroglobulin cleared rapidly (t 1/2 = 3 min), and this clearance was inhibited by a 1000-fold molar excess of human alpha 2M-methylamine. Ovomacroglobulin-trypsin did not inhibit the binding of 0.2 nM 125I-labeled human alpha 2M-methylamine to mouse peritoneal macrophages in vitro, but chicken alpha M reacted with trypsin inhibited the binding by 50% at 1.9 nM. A kappa I of 1.1 nM was calculated for the binding of chicken alpha M-trypsin to the mammalian alpha-macroglobulin receptor. This affinity is comparable to that obtained with human and bovine alpha 2M.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008259:Macroglobulins / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000378:metabolism*
D000596:Amino Acids; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008259:Macroglobulins; D011971:Receptors, Immunologic; D000511:alpha-Macroglobulins; C036828:ovomacroglobulin; D014357:Trypsin