Day 10, Lecture 1: Proteins I: Protein structure-Function

Question 1

Question 2

Amino acids with special features?

Answer 2

• Glycine
  
  • A hydrogen side chain
  • small, thus no steric hindrance
  • can pack tightly
• Disulfide link
  
  • Crosslink two cysteine (C) groups to join polypeptides together
• Proline
  
  • A secondary amine with a ring; kinks polypeptide chain

Question 3

Question 4

The formation of the amide or peptide bond occurs in the

Answer 4

ribosome

Question 5

The peptide bond can _____ with other peptide bonds and groups

Answer 5

Hydrogen bond

Question 6

In a polypeptide chain, the only rotation is around the _____. Due to

Answer 6

• Alpha-carbon
  
  • due to steric hindrance and/or interactions between R-groups, only certain favorable angles are allowed between any two residues

Question 7

Answer 7

Question 8

Question 9

Isoforms/isozymes

Answer 9

proteins with distinct sequences that perform the same general function. Optimize performance for functions in other tissues or developmental stages

Question 10

all peptide bonds are ____ bonding in alpha helix and beta sheets

Answer 10

hydrogen bonding

Question 11

common amino residues in turns

Answer 11

• glycine, good since no side group
• proline, starts a kink for a tight turn

Question 12

Motifs

Answer 12

combinations of helix, sheet, etc structures

Question 13

Denaturing proteins using

Answer 13

• Heat
• pH changes
• Solvent change (turn protein hydrophobic core inside out)
• Toxic ligans (heavy metals can disrupt disulfide links)

Question 14

Osteogenesis imperfecta

Answer 14

• In some cases, results from a point mutation that changes glycine ot a bulky amino acid that impairs triple helix formation. Strong collagen fibers do not form resulting in “brittle bone disease)

Question 15

Conformational change of protein can result in change of function such as

Answer 15

• Control activity
  
  • protein off or on depending on a phosphorylation event that changes tertiary structure
• Fine-tune function
• Accommodate several types of molecules
  
  • enzyme can accept a substrate and release a product
• Convey information
  
  • hormone in blood binds to a cell surface receptor that starts a signaling cascade in the cell cytoplasm

Question 16

Severe hemophilia A

Answer 16

• in some cases, is the result when one of the Arginines at positions 1689 or 372 of Factor VIII is mutated to another residue that cannot be clipped by the protease thrombin; therefore VIII is transformed into the useful form

Question 17

Sickle Cell anemia A

Answer 17

• Results for a defect in hemoglobin [Hb] beta subunit chain in which glutamic acid #6 has been converted to valine )(HbS) as a result of an A to T point mutation. This forms a “sticky” spot that allows the deoxy form of HbS to polymerize distoring the red blood cell shape

Question 18

G6PDH deficiency

Answer 18

• Results form numerous missense mutations of this X-linked gene
• results in an unstbale protein with shorter half-life
• therefore, the cells have low amounts of NADPH and glutathione to counteract oxidation products

Question 19

The critical features of polypeptide structure and of _____ interactions govern folding

Answer 19

bonding interactions