Three different approaches were used in an attempt to characterize the KB-cell receptor for adenovirus: affinity chromatography, immunoadsorption and cross-linking with a cleavable bifunctional reagent. The first system used an affinity gel consisting of adenovirus-fibre projection linked to Sepharose matrix by an intermediate bis(aminopropyl)amine arm, the amino groups of the fibre ligand being preserved by prior citraconylation. The second system consisted of adenovirus complete penton capsomere attached to anti-(penton base) antibody and cross-linked to polyacrylamide particles with glutaraldehyde. In this latter affinity model, the penton-fibre projection was appropriately oriented outwards, as in the virus particle. Both affinity systems permitted isolation from a KB-cell plasma-membrane extract of fibre-binding and penton-fibre-binding protein material, which inhibited adenovirus attachment. The penton–immunoadsorbent appeared more efficient and more specific than the affinity column of fibre–bis(aminopropyl)amino-Sepharose gel in specific activity of inhibition of adenovirus attachment. The third method consisted of reversibly cross-linking KB-cell receptor proteins with adenovirus particles by means of a cleavable di-imidoester and isolation of the complexes by sucrose-density-gradient centrifugation. Polypeptide analysis on sodium dodecyl sulphate/polyacrylamide gel of labelled KB-cell surface proteins, selected by the different procedures, showed that three major protein subunits of 78000, 42000 and 34000mol.wt. were common to the three selection systems. A possible model for the structure and function of the KB-cell receptor for adenovirus is discussed.

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