Cell Biology: Bio308 Review 1 September 2001

The review is due Friday September 28th, 2001 at 3:00pm

(If you chose the ‘early’ option the review is due Sunday September 23rd at 3pm.)

This is a closed-book, closed-note review. The review was designed to be completed in 2 hours but, other than the final due time, you have is no time limit when taking it. All answers must be typed and must be in the form of complete sentences unless the question specifically states otherwise. You may use a calculator if calculations are required. However, the steps behind any calculation must be included to receive full credit (can be hand-written). If required, or used to clarify a point, any figures or graphs may be hand-drawn.

The questions are yours to keep. This page must be the first page of your answer packet. Fill out the information at the bottom and attach this page to the ones containing your answers.

The top of each additional page in the packet should contain only your initials and the page number.

Your review period does not begin until you read any question within this packet.

Any questions about the review should be directed to me at kabernd@davidson.edu, 894-2889 (o), or xxxxxxx (h). Any calls to my home must occur before 9:00pm.

Turn in the review at my office (Watson 289). Sign the sheet on the door and place the review either in my hands or under my door. Your card access will allow you to turn in the review ‘after hours’.

Name: ____________________________________


Signature: ???????_________________________________

My signature indicates that I have completed this review following the Honor Code.

This review was completed in ________hours

I attended Dr McCartney’s seminar ____, The Sunday concert____, The Drug launch __

On this review there are 20 questions worth a total of 100points and 3 bonus point ‘attendance opportunities’.

The protein and information provided is ‘real’. Read it carefully and use it to aid answering the questions.

The September 7th 2001 issue of the journal Science includes an article by G. Chang and C.B. Roth reporting the structures of the MsbA protein. MsbA is a protein found in the bacterium, E. coli and is a member of the ABC Binding Cassette Transporter protein superfamily. This family of proteins has ‘relatives’ in yeast and mammals. In humans, faulty ABC Binding Cassette proteins have been implicated in cystic fibrosis, immune disorders and cancers that are resistant to chemotherapeutic drugs.

It had previously been predicted, and this paper shows, that the MsbA protein contains 3 distinct types of domains. It acts as a dimmer. Each monomer contains six transmembrane alpha helices in a membrane spanning domain, two domains containing ATPase activity and one substrate binding domain.

1. Describe the highest level of protein structure demonstrated by the functional form of this ABC binding cassette protein. (3pt)

2. Describe an alpha helix and predict the types of amino acids found in MsbA’s alpha helical domains?(6pt) (Support your prediction) Specific amino acids may be used as examples but relevant general characteristics of the amino acids are sufficient.

3. Applying information from our discussion of GTPases, what type of reaction is catalyzed by the ATPase domains? (Be sure to mention the substrate of the reaction) (4pt)

In E. coli, MsbA dimers transport a molecule called lipid A from the cytosolic side to extracellular side of the plasma membrane.

4. Where in the cell do you predict the ATPase domains of MsbA are located? (Support your prediction) (4pt)

5. What are the main components of a biological membrane and how do they contribute to the membrane’s function? (Answer in no more than 50 words)(6pt)

6. Given what you know about the structure/function of biological membranes and this introduction to MsbA, predict and discuss the relevance of each of MsbA’s 3 different types of domains for the dimer’s correct function. (15pt) (250 words maximum)

7. This article by Chang and Roth represents years of painstaking research focused on a protein that transports a lipid in a bacteria. ABC binding cassette transporters are implicated in many human diseases that would seem to be more ‘pressing’ avenues of research. Why study MsbA? (4pt)

Another member of the ABC binding cassette transporter protein superfamily is the yeast protein Ste6. Ste6 transports a factor from the cytosol to the outside of the cell.

8. Where in the cell is the Ste6 gene located? (2pt)

9.What is the scientific name of brewer’s yeast? (2pt)

10. Which mating type(s) of yeast express a factor? (2pt)

11. a factor is an example of an anti-mitogen. What is an anti-mitogen? What is differentiation? How could an anti-mitogen lead to differentiation? (7pt)

You have free time in lab and decide to compare gene expression in cells, alpha cells and a/alpha cells.You have unlimited time and laboratory resources. Your goal is to look at Ste6 mRNA in each cell type.

12. To reach your goal you can perform SDS-PAGE, light microscopy, a Dot blot, a Northern blot, or a Southern blot. Which method(s) will provide the information you seek? Provide a one-sentence description for the method(s) you chose. (5pt)

13. Discuss the results you predict for each cell type. (6pt)

The yeast mating response signaling pathway is activated by events at the cell surface that are identical to those seen in normal stimulation of the thyroid.

14. Name and compare and contrast the type of extracellular communication used to elicit the mating response and to stimulate the thyroid (in a normal person). (10pt)

15. Given the overlap in mechanism of initial activation in these two signaling cascades, what type of receptor is involved in the yeast mating response? (Support your answer) (4pt)

16. Briefly describe two other types of cell surface receptors and how they ‘pass messages’ to the cytosol. (No more than 50 words for each type) (7pt)

17. The initial activation step in the yeast mating response and in thyroid stimulation involve the same type of signal molecule and the same type of receptor. Why is it that yeast get ready to mate, why doesn’t the signal cause the yeast to make thyroid hormone? (5pt)

The thyroid hormones T4 and T3 affect the metabolism of many cells within the body. These hormones are not steroids but they interact with target cells the same way that steroids do.

18. Where in the cell are steroid receptors located? (2pt)

19. Why was the true molecular basis of Graves’ disease unexpected? (3pt)

20. Molecular mimicry has been invoked as the reason why some people develop Graves’ Disease. What is molecular mimicry and how could this result in thyroid problems? (3pt)