1. How many ammino acids are in this peptide? 2. Some proteins are composed prim

Question

1. How many ammino acids are in this peptide?

2. Some proteins are composed primarily of ?-sheets that form themselves into a cylindrical structure called a ?-barrel. The ?-barrel is commonly found embedded in a membrane and is used as a tunnel of sorts to allow hydrophilic molecules to pass through the membrane. The R-groups of the amino acids that line the lumen of the barrel are typically hydrophilic, whereas the R-groups of the amino acids that are in contact with the phospholipid bilayer are typically hydrophobic. Knowing this, and taking into account how R-groups are arranged in a ?-sheet, which of the following amino acid sequences is likely to be part of a ?-sheet that forms a ?-barrel? Note – The letters below are the one-letter abbreviations for amino acids.

A. D K L V T S I A R E F M

B. T L N I S F Q M E L D V

C. D C S L A I L W Y T E V

D. M L E F M D I A S V L D

E. D S E T K N A V F L I L

3. In its phosphorylated state, Tig-4 inhibits an enzyme called Kom-3 (fictional), which converts glutamine to glutamic acid. When Tig-4 is unphosphorylated, it is unable to inhibit Kom-3. Also, at high concentrations, glutamine binds to NC-1 rendering it inactive. When glutamine concentrations drop, NC-1 is again able to phosphorylate Tig-4. Answer the questions below. *Hint: Draw the interactions out on paper to get a “big picture” view of the metabolic pathway described. Use lines with arrows (?) to indicate activating events. Use lines with perpendicular bars (- -|) to indicate deactivating or inhibiting events.

A. What type of allosteric regulation characterizes the phosphorylation of Tig-4 by NC-1, positive or negative? B. What type of allosteric regulation characterizes the binding of glutamine to NC-1, positive or negative?

C. In 1-2 sentences, describe how an absence of ATP would affect the production of glutamic acid in this metabolic pathway.

Explanation / Answer

1) 9 AMINO ACIDS ARE PRESENT ( NO.OF AMIDE BONDS +1)

AMINE BONDS REPRESENT WITH YELLOW BOXES

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