1. How is RNase A different from most other proteins?
2. Why isn't RNase A suitable for cancer treatment?
3. Click on the Protopedia link and read the seed article. What is one amino acid residue required for RNase catalytic activity?
4. Go back to the Protein Data Bank and click on PDB entry 54sa to see more details about the structure of RNase A. On the structure diagram, what are the little molecules shown clustering around the ribbon diagram?
Hint: scroll down the page and check the ligands.
5. Click on the Sequence Details tab at the top of the page. Are more residues in RNase A part of alpha helices or beta-pleated sheets?

This is due at the beginning of class on Wednesday. Answers must be turned in individually.

Answers:

1. It is exceptionally stable to denaturing conditions, including acid and heat.

2. It breaks down RNA molecules inside cells, which means it's very toxic for cells.

3. Histidine or lysine (both answers are acceptable).

4. Deuterated H₂O (There are also phosphates, but not nearly as many.)

5. Beta-pleated sheets (38% β vs. 20% α-helices)

Comments after grading: I discovered while grading these that it's so tempting to put in all possible answers, and I had failed to say ahead of time that I value the ability to choose the most appropriate answer.

So, including additional answers (such as the fact that RNase A cuts in the middle of RNA rather than at the end) resulted in losing 0.5 point. If possible, I will create six assignment during the semester and drop one, which will provide a little more flexibility.

My goals with the assignments are to introduce additional sources of information and also to provide encouragement (see what you can understand, now?). At the same time, I want to encourage you to be selective and learn to recognize the best answer.

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