Gene Expression of a Protein, JB70, Related to Rat α1-Acid Glycoprotein inEuglena gracilis

Antibodies directed against rat alpha1-acid glycoprotein (AGP) recognize a 70 kDa antigen, designated JB70, present in extracts of achlorophyllous Euglena gracilis cells as well as in their culture medium. By using 2-dimensional electrophoresis, JB70 appears to be composed of two acidic polypeptides. Additionally, Northern blot analysis reveals the presence in E. gracilis cells of a 2.3 kb mRNA hybridizing with a cDNA probe specific for rat AGP mRNA. Moreover, elevated mRNA levels are detected in dexamethasone-treated E. gracilis cells, indicating a response to this inducer similar to that observed for hepatic AGP. These results strongly suggest that polypeptides closely related to hepatic rat AGP are expressed in E. gracilis cells. They also indicate that, like other gene families implicated in natural defense processes such as heat-shock protein and metallothionein genes, the AGP gene appears to be conserved down to this early diverging eucaryote.