CH3F5 Question 6 Answers 2015-16 PDF

CH3CHA SECTION B: BIOORGANIC CHEMISTRY (CH3F5) Answer ONLY TWO Questions from Questions 4, 5 and 6 6. Answer ALL PARTS. (a) Explain briefly the importance of the hydrophobic effect in the folding of soluble, globular proteins. [20%] 4 marks From lectures: In simple terms: non-polar amino acids drive...

CH3CHA SECTION B: BIOORGANIC CHEMISTRY (CH3F5) Answer ONLY TWO Questions from Questions 4, 5 and 6 6. Answer ALL PARTS. (a) Explain briefly the importance of the hydrophobic effect in the folding of soluble, globular proteins. [20%] 4 marks From lectures: In simple terms: non-polar amino acids drive the folding of globular proteins by release of water (classical hydrophobic effect) leaving polar and charged residues on surface of protein. Mention of C Anfinsen’s work on ribonuclease would be suitable example, but not required for full marks. Brief discussion of nucleation of secondary structure and cooperativity leading to a ‘folding funnel’ in the energy landscape - - hydrophobic effect assists in overall driving force. (b) Explain using a suitable model how and why the correct folding of membranebound proteins differs from soluble, globular proteins. [30%] 6 marks From Lecture 17 specifically. Apolar membrane environment means that evolved protein structures typically have facial amphiphilic character supporting the binding of helices to one another via two-stage folding process (this is the ‘suitable model’ expected). Shape selective (‘knobs-into-holes’) packing then assists the correct assembly of tertiary and quaternary structure. Mention of helical wheel diagrams in predicting which resides are significant in interacting helices. Specific example not required, but mention of e.g. GPCR or other membrane protein and a suitable view of phospholipid bilayer schematic would be expected for full marks. Marks awarded flexibly for all reasonable discussion and examples provided in either (a) or (b). 6