Effect of serum albumin on the recovery of human IgA1 from immobilized jacalin.
Published methods for affinity purification of human IgA1 on immobilized jacalin are based on binding through galNac residues in the IgA1 hinge region. The present study shows that in addition to this galNac-dependent binding an 'alternative' binding mechanism, involving protein-protein interactions, is operative. Moreover, human (HSA) and bovine (BSA) serum albumins were also observed to interact with jacalin through the 'alternative' mechanism, though much more weakly than IgA1. HSA and BSA did not interfere with the galNac-dependent binding of IgA1, but inhibited the 'alternative' binding of IgA1 to jacalin-Sepharose, probably by competition. Thus, IgA1 from serum samples was almost completely bound through the galNac-dependent mechanism, but part of the IgA1 from samples containing little or no HSA or BSA was bound by the 'alternative' mechanism. Washing of jacalin-Sepharose columns with excess BSA could disrupt the 'alternative' binding and subsequent washing with 0.8 M D-galactose in 0.5 M NaCl/PBS was sufficient to elute all IgA1. The 'alternative' binding to jacalin is probably not restricted to the above-mentioned proteins. Purification of IgA1 by precipitation with jacalin and subsequent gel filtration of the D-galactose-dissolved precipitate was not practical, since jacalin-IgA1 precipitates did not dissolve completely and new complexes were formed during the gel filtration procedure.
Biewenga
J
J
Department of Cell Biology, Free University, Amsterdam, The Netherlands.
Steneker
I
I
Hameleers
D M
DM
D001666:Binding Sites, Antibody; D002846:Chromatography, Affinity / Q000379:methods; D002850:Chromatography, Gel; D004347:Drug Interactions; D006801:Humans; D007070:Immunoglobulin A / Q000302:isolation & purification*; D007202:Indicators and Reagents; D037102:Lectins; D009194:Myeloma Proteins / Q000302:isolation & purification; D037121:Plant Lectins; D011233:Precipitin Tests; D012709:Serum Albumin; D012710:Serum Albumin, Bovine
D007070:Immunoglobulin A; D007202:Indicators and Reagents; D037102:Lectins; D009194:Myeloma Proteins; D037121:Plant Lectins; D012709:Serum Albumin; C043696:jacalin; D012710:Serum Albumin, Bovine