16 Jun Human-growth hormone binds to two different
Question
So I have a couple questions from my chemistry class. Its an advanced college course and the professor made the questions that follow with all the intention of challenging anyone with chemical and biochemical background. Any help will be greatly appreciated.
1. Human-growth hormone binds to two different receptors, one of which also binds the hormone prolactin. Studies revealed that the growth-hormone-prolactin receptor interaction is weak in the presence of EDTA, but increases 8,000-fold upon the addition of 50 µM zinc. Mutagenesis studies indicated that changing His18, His21, or Glu174 in growth hormone to alanine reduced the strength of this interaction by two orders of magnitude. Even larger effects were observed following mutation of His188 in the prolactin receptor to alanine. Propose a model to account for these observations.
2. Suggest possible reasons why trivalent ions, such as Fe(III) or Mn(III), have not been widely utilized in hydrolytic metalloenzymes for substrate binding and activation.
3. Some proteases, such as chymotrypsin, do not contain metal ions in their active sites. Instead, there are several other functionalities that facilitate peptide bond cleavage. The reaction proceeds through nucleophilic attack of a serine hydroxyl on the peptide carbonyl group. The carbonyl group of the substrate is positioned near a cluster of peptide NH moieties. Compare the roles that these groups might play in catalysis with those of zinc in carboxypeptidase.
4. The cytochromes P450 are regarded as oxidizing enzymes; yet they consume one equivalent of NADH for each catalytic cycle. Why is NADH required? What atoms are formally reduced in the overall reaction?
5. The metal-binding selectivity of the copper protein azurin has been probed by using scanning calorimetry. In this method the temperature of a sample containing the protein is raised, and the amount of heat absorbed is monitored. At a certain temperature, corresponding to that at which the protein “melts”, a large ampunt of heat is absorbed. For native, Cu(II) azurin, a total of 21 cal/g of heat is absorbed. For Ni(II) substituted azurin, only 10 cal/g are absorbed. Which metal is bound more tighty? Explain the difference in terms of ligand field stabilization.
Tutorials for this Question
Our website has a team of professional writers who can help you write any of your homework. They will write your papers from scratch. We also have a team of editors just to make sure all papers are of HIGH QUALITY & PLAGIARISM FREE. To make an Order you only need to click Ask A Question and we will direct you to our Order Page at WriteDemy. Then fill Our Order Form with all your assignment instructions. Select your deadline and pay for your paper. You will get it few hours before your set deadline.
Fill in all the assignment paper details that are required in the order form with the standard information being the page count, deadline, academic level and type of paper. It is advisable to have this information at hand so that you can quickly fill in the necessary information needed in the form for the essay writer to be immediately assigned to your writing project. Make payment for the custom essay order to enable us to assign a suitable writer to your order. Payments are made through Paypal on a secured billing page. Finally, sit back and relax.
About Writedemy
We are a professional paper writing website. If you have searched a question and bumped into our website just know you are in the right place to get help in your coursework. We offer HIGH QUALITY & PLAGIARISM FREE Papers.
How It Works
To make an Order you only need to click on “Order Now” and we will direct you to our Order Page. Fill Our Order Form with all your assignment instructions. Select your deadline and pay for your paper. You will get it few hours before your set deadline.
Are there Discounts?
All new clients are eligible for 20% off in their first Order. Our payment method is safe and secure.