03-11-2008, 11:30 AM
An immigrant family from rural Mexico brings their 3-month-old child to the emergency room because of whistling inspiration (stridor) and high fever. The child's physician is perplexed because the throat examination shows a gray membrane almost occluding the larynx. A senior physician recognizes diphtheria, now rare in immunized populations. The child is intubated, antitoxin is administered, and antibiotic therapy is initiated. Diphtheria toxin is often lethal in unimmunized persons because it
A. Inhibits initiation of protein synthesis by preventing the binding of GTP to the 40S ribosomal subunit
B. Binds to the signal recognition particle receptor on the cytoplasmic face of the endoplasmic reticulum receptor
C. Shuts off signal peptidase
D. Blocks elongation of proteins by inactivating elongation factor 2 (EF-2, or translocase)
E. Causes deletions of amino acid by speeding up the movement of peptidyl-tRNA from the A site to the P site
A. Inhibits initiation of protein synthesis by preventing the binding of GTP to the 40S ribosomal subunit
B. Binds to the signal recognition particle receptor on the cytoplasmic face of the endoplasmic reticulum receptor
C. Shuts off signal peptidase
D. Blocks elongation of proteins by inactivating elongation factor 2 (EF-2, or translocase)
E. Causes deletions of amino acid by speeding up the movement of peptidyl-tRNA from the A site to the P site