Microtubules carrying GDP at their ends are more likely to lose tubu- lin monomers. Show how these facts can explain the remarkable observation that at certain GTP levels some microtubules in a mixture will grow while others simultaneously shrink. Tubulin binds GTP, and the polymerization of a microtubule is greatly stimulated when a tubulin molecule at the growing end carries GTP. Tubulin also has a GTPase activity, with a low-turnover number.

8) A Leu > Ala mutation at a site buried in the core of the enzyme lysozyme ends up being destabilizing. Explain why in terms of AH", AS" (for both the protein and solvent), and AG".

PfCRT is found to have 10 peaks on a hydropathy plot given its primary sequence. Researchers also noted that each peak is comprised of about 30 amino acids. The digestive vacuole membrane is 45Å in Plasmodium species. Explain why researchers conclude there are 10 transmembrane helices from these two pieces of data.

Propose an experimental strategy to characterize the sequence and linkages of different glycan subtypes that comprise the glycome. For example, how might protein-associated N- and O-glycans be structurally characterized?

Specificity in fusion between vesicles involves two discrete and sequential processes. Describe the first of the two processes and its regulation by GTPase switch proteins. What effect on the size of early endosomes might result from overexpression of a mutant form of Rab5 that is stuck in the GTP-bound state?

You are studying how your Lys-Val-Thr tripep de interacts with another pep de, which places an Asp in close proximity to the Lys on your pep de. How would the presence of an Asp side chain affect the pKa of the Lys side chain? Briefly explain your reasoning. (remember pKas are rela ve, pKa=log([H+][A-]/[HA])

What is the pelleting time for eukaryotic ribosome subunits, 40S and 60S, in a rotor with k = 180? Assume that the medium viscosity and density are similar to water at %3D 20°C.

1 2 Glycogenin is a homodimer of 37 kDa subunits. (Homodimer means identical subunits of type a that form a dimer of type a2). Glycogenin has a chain of a(1,4)-linked units of glucose attached to the sidechain of a tyrosine residue. The chain of a(1,4)-linked glucose units is a primer for the initiation of glycogen synthesis by glycogen synthase. Assume the dimer is stable and not in equilibrium with monomer subunits. Which of the answers below are plausible pathways for attaching or building the primer chain of glucose units? The branching enzyme attaches a chain of 7 glucose units to the tyrosine sidechain of glycogenin. 0 0 0 0 000 The transferase attaches 3 units of a(1,4)-linked glucose to the tyrosine sidechain of glycogenin. Glycogen synthase then extends the chain using UDP-Glc. 0 One glycogenin dimer builds the a(1,4)-llinked glucose chain on a subunit of another glycogenin dimer. -D-O Each subunit builds the a(1,4)-Ilinked glucose chain on the other subunit of the same dimer.…

(a) You have found a new, enhanced version of the drug jafrasitor, (called jafrasitorplus) (molecular weight 600 grams/mol), that binds the histone deacetylase enzyme Sir2 with a dissociation constant KD = 0.03 nM. What mass of jafrasitorplus should be administered to a patient with a blood volume of 5.5 L such that Sir2 is at least 91% inhibited? Show your work and reasoning.

Bovine insulin is composed of two polypeptide chains that are linked together covalently. The two chains have the following sequences: GIVEQCCASVCSLYQLENYCN - A chain FVNQHLCGSHLVEALYLVCGERGFFYTPKA - B chain a. Through which amino acids are these two chains linked together covalently? b. How many different ways can these two chains be linked? c. Of the different connectivities you enumerated in part b, which is the biologically active form?