Treating a solution of ribonuclease with 2-mercaptoethanol and urea denatures the enzyme. If the 2-mercaptoethanol is removed, followed by the removal of urea, the ability of the enzyme solution to hydrolyse RNA is reduced by about 99%. What is the most plausible explanation for this observation?   a. All of the RNase molecules have about 1% of their usual activity, due to changes to the organisation of disulphide bonds   b. Random formation of disulphide bonds mean about 1% of the RNase molecules are 100% active whereas 99% have no activity   c. Deprotonation of histidine in the active site of the enzyme means that only about 1% of the enzyme molecules are active   d. Deprotonation of histidine in the active site of the enzyme means that all

1. why is the ribosome a good drug target? 2. Tetracyclines: a. Where do first generation tetracyclines bind? b. Which step in protein translation do they inhibit? C. Why was it necessary to come out with a third generation tetracycline, and how are they different? 3. What are three ways that 2-deoxystreptamine (2-DOS) aminoglycosides can inhibit protein synthesis? 4. Chloramphenicol: a. Where does this drug bind? b. How does it inhibit protein synthesis?

A ribonuclease reaction containing 0.50µM RNASE A will hydrolyze RNA at a maximal rate of 5µM/s in the presence of 40mM RNA at 37°C. What is the turnover number, kcat, for the enzyme (per second).

Consider the mechanism of the enzyme RNase:   What would happen to the Km (i.e., would it increase, decrease, or stay the same) if the his12 was mutated to a lysine? Explain.   What would happen to the Kcat (i.e., would it increase, decrease, or stay the same) if the his12 was mutated to a valine? Explain.

In studies using repeating copolymers, AC . . . incorporates threonine and histidine, and CAACAA . . . incorporates glutamine, asparagine, and threonine. What triplet code can definitely be assigned to threonine?

The biosynthetic pathway for the two amino acides E and H is shown schematically in the Figure below: A W E 2 Z H How would this pathway change if C was mutated and non-functional?

Posttranslational modifications of proteins do not include: peptide bond formation glycosylation acetylation of N-terminal peptide bond cleavage disulfide bond formation QUESTION 16 14 15 16 streptomycin puromycin 17 18 19 20 Which one of the following antibiotics does NOT function by interfering with the translational/post-translation process tunicamycin penicillin O tetracyclin O O

Given the following diagram of how protein AWESOME1 binds to it's target DNA, describe the potential effects of each of the 5 mutations shown below. The wild-type sequence of a helix #1 is also shown in the blue box, and all the mutations are in helix #1 (see numbers for identifying particular residues). a helix #1 R(1)-V-I-L-Y-F-W-I-M-Y-F-S-H-Y-W-R(16) #1 Predict the consequence of the following mutations: 1) Arg(1) to Glu 2) Arg(1) to Ala 3) Phe(6) to lle 4) Trp(7) to Phe 5) Met(9) to Pro in