Amino acids, peptides, proteins III

Question 1

2 major classes of tertiary structures

Answer 1

Fibrous

Globular

Question 2

Fibrous tertiary structures

Answer 2

Tend to be long and composed of only alpha-helices or beta-sheets.
They are insoluble.
Important for structure or protection.

Question 3

Globular tertiary structures

Answer 3

Most proteins in body
Water or lipid soluble
Carry out diverse functions!
Turns or loops are important in the structure of globular proteins. Enable polypeptide chain to form particular structures instead of staying extended linear.
Important function of these proteins is to interact with or bind other molecules.

Question 4

Most frequent AA’s in loops and turns?

Answer 4

Glycine and Proline

Question 5

Quaternary Structure

Answer 5

Sometimes more than one polypeptide chain come together to form quaternary structures.
For example, four polypeptide chains come together to form a functional hemoglobin.

Question 6

Different proteins

Common structural motifs

Answer 6

Different proteins sometimes use common structural motifs which are specific arrangements of secondary structure elements.
Common structural motifs often carry out similar functions. Many proteins are composed of domains which are often independent folding and functional units.

Question 7

Kd

Answer 7

The binding strength is often represented by dissociation constant Kd. The binding specificity is achieved through the lock and key complementary model or the induced fit model.

HIGHER number means it is bound less tightly (easier to dissociate)

Question 8

Hemoglobin, CO, and myoglobin

Answer 8

Carbon monoxide binds heme much tighter than oxygen, leading to CO poisoning.
Myoglobin can only store but cannot transport oxygen. Hemoglobin, on the other hand, has a quaternary structure composed of four poly peptide chains.

The heme binding sites in these four chains interact with each other which enables Hb to have a Tense and Relaxed state with different oxygen binding affinities. These unique structure and binding properties enable hemoglobin to bind oxygen tightly in the lung and release the oxygen in tissues.

Question 9

How do you determine protein structure?

Answer 9

Crystallography
NMR: resonance signal
Structure important for understanding fx/ drug desing