protein quarternary structure

Question 1

what are some direct methods for intact complexes

Answer 1

• light scattering
• size exclusion chromatography
• dual polarisation interferometry
• sedimentation-equilibrium ultracentrifugation

Question 2

what are some indirect methods for intact complexes

Answer 2

• ultracentrifugation (sedimentation velocity)
• light scattering
• pulsed gradient NMR
• fluorescence polarisation
• dielectric relaxation

Question 3

what are the benefits of quartnerary structure in enzymes?

Answer 3

• allows multifunctional enzymes
• separates catalytic and regulatory functions
• allows cooperativity of substrate binding

they can also decrease the diffusion path of a labile intermediate

Question 4

describe the general features of a fibrous protein

Answer 4

• highly elongated polypeptides
• single secondary structural characteristic
• primary component of bone, tendon, skin, connective tissue
• structural material

fibrous proteins are known as scleroproteins

Question 5

what are the three types of proteins

Answer 5

• globular
• fibrous
• membrane

Question 6

describe the key features of collagen

Answer 6

• major component of skin, ligaments and cartilage
• most abundant protein in the human body
• long rigid structure
• monomers form a tight helix

Question 7

describe the structure of collagen

Answer 7

• hydrogen bonds within strands are absent, strands are instead held together by steric repulsion
• 3 strands wind around each other forming a superhelical cable
• H bonds form between NH groups of glycine and CO groups in other residues in different chains

Question 8

describe the general features of elastin

Answer 8

• protein critical to the elasticity and resilience of many vertebrate tissues
• synthesised from a precursor tropoelastin
• rich in proline and lysine

Question 9

what are the three types of fibrous proteins

Answer 9

• collagen
• elastin
• keratin

Question 10

describe the key features of keratin

Answer 10

• mechanically durable
• makes up 85% of hair, nails, feathers and horn
• constructed of a left-handed superhelix called an alpha helical coiled coil

Question 11

describe the structure of keratin

Answer 11

• complex quarternary structure
• dimers composed of a type I and type II subunit
• dimers associate to form protofilaments
• protofilaments dimerize to form protofibrils
• protofibrils form tetramers called microfibrils
• microfibrils associate into macrofibrils