Exam (elaborations)
exam molecular biology
molecular biology of the cell
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Seller
Follow
Content preview
Side 1 af 10Answers for Exam - BMB508/BMB809,
June 6. 2012
Please note that the answers given are not the only way to answer correctly. It is possible to
provide correct answers, which are shorter and less comprehensive than the answers given
here. So please regard this as a guide to what should be included in the answers and not the
only correct way to answer.
, Side 2 af 10
Question 1. Inherited disease, cancer and G-proteins - (35%).
Costello syndrome is an inherited disease with many symptoms including overgrowth of the skin and
mental retardation. Costello syndrome is caused by mutations in the Ras gene of the Ras-MAPK
signaling pathway. The Ras-MAPK pathway can be activated by receptor tyrosine kinases (RTKs).
1. Give a brief description of RTKs and explain one main difference between RTKs and cytokine
receptors in the cytosolic part of the receptors.
Receptor tyrosine kinases (RTKs) are receptors located on the surface of the cell, which bind various
ligands, like growth factors. RTKs have an intrinsic tyrosine kinase in the cytosolic domain. In the
unbound state RTKs are monomers, with very low tyrosine kinase activity. When a ligand binds it
induces a conformational change which leads to formation of dimeric RTKs. In the dimeric RTKs the
tyrosine kinase on each monomer can phosphorylate an important tyrosine residue in the activation
lip of the other monomer (cross-phosphorylation). This causes the activation lip to move out of the
active site and allows binding of ATP or protein substrates. The activated kinases then phosphorylate
other tyrosine residues in the cytosolic domain and thereby allows docking/binding of signal
transducing proteins (like GRB2) with PTB or SH2 domains to the receptor. The dimeric RTKs typically
consist of two different monomers (For instance HER2/HER4).
In contrast cytokine receptor dimers are homodimers of the same monomer, also when they are
inactive. The cytokine receptors do not have an intrinsic kinase activity, but instead the cytosolic
domain of cytokine receptors associate with a JAK kinase. Ligand binding to the inactive
homodimeric receptor induces a conformational change which brings the associated JAK kinases
close to each other and allows cross phosphorylation and activation. Phosphorylation of tyrosines in
the cytosolic domain of the cytokine receptor allows STAT transcription factors and other signaling
molecules with SH2 or PTB domains to bind and be activated.
2. In figure A shown below the Ras-MAPK pathway is depicted. Describe the pathway and explain
what takes place at points 1-6 (black boxes).
FIGURE A.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Sameer420. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £7.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
61001 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now