Download CHEM 482

CHEM 482
Homework #1
Spring, 2008
_______________________Name
This assignment is worth 25 points. Please answer completely and make sure you address the
question—no beating around the bush
1. What is the polypeptide specified by the following DNA antisense strand? Assume translation
starts after the first initiation codon and continues until a stop.
5’-TCTGACTATTGAGCTCTCTGGCACATAGCA-3’
2. Why do oligonucleotides containing Shine-Delgarno sequences inhibit translation in
prokaryotes? Why don’t they do the same thing in eukaryotes?
3. Why does m7GTP inhibit translation in eukaryotes? Why doesn’t it do so in prokaryotes?
4. What is the energetic cost, in ATPs, for the E. coli synthesis of a polypeptide chain of 100 amino
acid residues starting from amino acids and mRNA? Assume that no losses are incurred as a result
of proofreading.
5. An antibiotic named fixmycin, which was isolated from a fungus on ripe passion fruit, is
effective in curing many types of venereal disease. In characterizing fixmycin’s mode of action,
you have found that it is a bacterial translational inhibitor that binds exclusively to the large subunit
of E. coli ribosomes. The initiation of protein synthesis in the presence of fixmycin always results
in the generation of dipeptides that remain associated with the ribosome. Suggest a mode of action
for fixmycin.