You are examining the mutational changes that occurred in a breast cancer cell line. You discover that there is a mutation in the gene encoding selenoprotein translation factor B (SelB). Which of the following is most likely defective in these cells as a result of this mutation?
A) decreased bile acid synthesis
B) decreased glycogen synthesis
C) decreased reactive oxygen species generation by pancreatic mitochondria
D) increased fatty acid incorporation into triglycerides
E) increased rate of erythrocyte lysis

Question

Quizplus · Accepted Answer

Selenocysteine incorporation in eukaryotic proteins occurs cotranslationally at UGA codons (normally stop codons) via the interactions of a number of specialized proteins and protein complexes. One of the complexes required for this important modification is comprised of a selenocysteinyl tRNA [(Sec)-tRNA_(Ser)Sec] and its specific elongation factor identified as selenoprotein translation factor B (SelB). A particularly important eukaryotic selenoenzyme is glutathione peroxidase, GPx. The main biological role for GPx is to protect cells from oxidative damage, particularly from membrane lipoid peroxidation. Since erythrocytes are exposed to a highly oxidizing environment, the loss of function GPx activity would lead to increased hemolysis.

You Are Examining the Mutational Changes That Occurred in a Breast