Studies on the nature of microsome-bound substances involved in the biosynthesis of acidic glycoproteins of guinea-pig serum

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Abstract
In further studies on the biosynthesis of components of fraction I, an acidic glycoprotein-containing fraction from guinea-pig serum, an investigation was made of the substances bound to liver micrisomes that had earlier been implicated to participate in the synthesis of components of fraction I present in serum. These substances were normally liberated by ultrasonic vibrations. Antisera to subtractions of fraction I were used for characterization. At pH8-6, most of the microsome-bound substances showed electrophoretic mobilities lower than components of fraction I but similar to components of sialic acid-free fraction I. On chromatography on Sephadex G-150, most of the microsomal substances were eluted at an essentially similar volume to the main components of fraction I. Most of the microsome-bound substances lack sialic acid residues, and, as appreciable degradation of completed molecules is unlikely, these substances appear to be precursors of serum glycoprotein molecules with incomplete prosthetic groups. Evidence was obtained on the submicrosomal localization of incomplete .and complete serum glycoprotein molecules.