Expression of Bovine β-Casein in Saccharomyces Cerevisiae and Characterization of the Protein Produced in Vivo

Rafael Jiménez-Flores, University of California - Davis
Thomas Richardson, University of California - Davis
Linda F. Bisson, University of California - Davis

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NOTE: At the time of publication, the author Rafael Jiménez-Flores was affiliated with the University of California, Davis. Currently, May 2008, he is Professor of Dairy Science at California Polytechnic State University - San Luis Obispo, CA.

Abstract

Recombinant DNA technology offers numerous opportunities for engineering food proteins and for studying their structure-function relationship. As part of the study of structure-function of bovine caseins, it is necessary to produce mutant proteins in experimental amounts and correlate their new structure to their physiochemical characteristics. To this end, bovine β-casein was expressed in the yeast Saccharomyces cerevisia by a fusion to the HXK1 (hexokinase P1) gene. Casein was produced during late exponential/early stationary phase of growth on glucose as would be predicted for a gene under the control of the HXK1 promoter. Bovine β-casein was posttranslationally modified by yeast. Internal phosphorylated forms were observed as well as a high molecular weight form that appeared to be O-glycosylated and largely localized to the periplasmic space.