Determination of dissociation constants and ligand specificity of detergent solubilized surface membrane immunoglobulin a from MOPC-315 |
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Authors: | Michael R. Jarvis Edward W. Voss |
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Affiliation: | Department of Microbiology, 407 South Goodwin, University of Illinois, Urbana, Illinois 61801, U.S.A. |
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Abstract: | Surface membrane immunoglobulin from MOPC-315 plasmacytoma cells (smM315) was isolated by nonionic detergent lysis of radioiodinated cells and affinity chromatography on Dnp-aminohexyl-Sepharose 4B. Verification of the solubilized molecule as an integral membrane protein, distinct from secreted MOPC-315 IgA (M315) was accomplished by NaDodSO?4-PAGE, charge-shift electrophoresis and molecular sieve gel filtration with NP-40 and deoxycholate. smM315 was compared to reduced and alkylated monomeric secreted immunoglobulins from MOPC-315, MOPC-460, and XRPC-25 by quantitative affinity chromatography (QAC) using two differently substituted Dnp-aminohexyl-Sepharose 4B resins. Unique patterns of cross-reactivity of all secreted myeloma proteins were independently established with a competitive hapten inhibition assay using 125I-Dnp26BSA as the precipitating probe. After derivation with dinitrobenzylsulfonate, Dnp-aminohexyl-Sepharose 4B was modified with succinic anhydride which, with the inclusion of 0.03% Doc in a PBS and 0.1% NP-40 buffer, prevented nonhapten specific protein-matrix interactions during QAC. Dissociation constants determined by QAC for three ligands, (dinitrophenyl-glycine, trinitrophenyl-amino-caproate and tetramethylrhodamine) were essentially the same for smM315 and M315. Both of the other nitrophenyl binding IgA myelomas had distinct and significant differences in dissociation constants. Thus, for a differentiated antibody secreting cell which has undergone a heavy chain class switch, such as MOPC-315, the cell surface immunoglobulin has an identical ligand binding active-site as the secreted immunoglobulin. |
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Keywords: | CHI competitive hapten inhibition QAC quantitative affinity chromatography Dnp 2,4 dinitrophenyl Tnp 2,4,6 trinitrophenyl TR tetramethylrhodamine gly glycine cap amino-caproate sm surfacemembrane Ig immunoglobulin smM315, surface membrane immunoglobulin from MOPC-315 M315 secreted immunoglobulin from MOPC-315 M460 secreted immunoglobulin from MOPC-460 X25 secreted immunoglobulin from XRPC-25 BSA bovine serum albumin KLH keyhole limpet hemocyanin NP-40 Nonidet P40 Doc deoxycholate PBS phosphate buffered saline PBS-det PBS with 0.1% NP-40 and 0.03% Doc glycoluril 1,3,4,6-tetrachloro-3,6αdiphenylglycoluril PMSF phenylmethylsulfonylfluoride sodium dodecyl sulfate-polyacrylamide gel electrophoresis a.m.w. apparent molecular weight |
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