6: Quaternary structure

BPG binds to _________ hemoglobin and not to _______ hemoglobin.

deoxy, oxy

This structure determination technique can produce structures at near atomic resolution.

Cryo electron Microscopy

Keratin contains a large number of hydroxylated __________.

None

A mature red blood cell is essentially just a sack of _________.

hemoglobin

A twisted sheet is typically formed by ___________ β-strands.

parallel

BPG makes hemoglobin a suitable transport protein of oxygen by ________ its affinity of oxygen.

decreasing

Myoglobin's function is to store/hold oxygen in muscle cells (myocytes). Its affinity for oxygen is ______ hemoglobin's affinity for oxygen.

Higher than

Collagen contains a large number of hydroxylated __________. You may select multiple answers.

Pro

________ collagen polypeptides twist together to make a right-handed helix.

3

The fibrous protein in hair is _________.

keratin

Strenuous exercise causes muscle to release lactic acid. In the blood lactic acid quickly converted to lactate and protons. This causes hemoglobin to _______.

Release oxygen

In going between deoxy and oxy hemoglobin _______ moves as a unit.

αβ subunits

Nature __________ adds/inserts domains (modules) into a variety of proteins to modify/modulate their functions

frequently

α helices with mainly polar residues are ______ helices.

polar

Myoglobin and subunits of hemoglobin have _______ folds.

similar

The protein diagramed above is an excellent example of a protein containing multiple ________.

domains

Antibodies can be generrated to multiple regions of antigenic protein.

True

The helices lying on the surface of an 8 strand β−α−β barrel are __________

Amphipathic

Residues participating in a protein-protein interface are largely ______.

Hydrophobic

The helices in collagen are α helices.

False

This molecule forms a triple helix.

collagen

When carbon dioxide reacts with water, bicarbonate and ______ are produced

H+

______ binds the iron ion in hemoglobin.

His

What is the quaternary structure of myoglobin?

α

α helices with mainly nonpolar residues on one side and polar residues on the other are ______ helices.

Amphipathic

Carbon dioxide is very soluble in blood.

False (wouldn't need to convert to bicarbonate)

What conformational changes occur when oxygen binds hemoglobin? You may select multiple answers.

1) One αβ dimer rotates 15º relative to the other αβ dimer.
2) The cavity at the center of the tetramer becomes smaller
3) The iron moves into the plane of the heme.
4) F helix containing His ligand for Fe pulled closer to E helix

α helices lying on the surface of a membrane are ________.

Amphipathic

Why can't myoglobin be used to transport oxygen from the lungs to the tissues?

Myoglobin binds oxygen too tightly

Approximately 25-30% of the protein in humans is collagen. Thus about __________ of all amino acids in proteins in human is hydroxyproline making it the most abundant modified amino acid.

9

In deoxyhemoglobin the iron ion is in the plane of the heme poyphryin rings.

False

Proteins typically fold to bury _______ residues in their cores.

Hydrophobic

Transporting of carbon dioxide from the tissues to the lungs is does NOT involve hemoglobin.

False

This molecule forms a triple helix.

collagen

Myoglobin and hemoglobin were among the very first proteins for which structures, albeit at low resolutions, were obtained.

True

2,3-bisphosphoglycerate (BPG) aids in the transport of oxygen by __________

Binding to deoxyhemoglobin

2,3-bisphosphoglycerate (BPG) _______.

Binds to deoxyhemoglobin tetramer

α helices with mainly nonpolar residues are ______ helices.

Hydrophobic

Each polypeptide of collagen has a __________.

left-handed twist

Three collagen polypeptides twist together to make a ______-handed helix.

Right

Keratin intermediate filaments contain chains held together by ______

Disulfide bonds

Globular proteins usually have _______ internal cavities.

No

Extended β-strands of L-amino/imino acids tend to have ________ twist.

Right-handed

What is NOT true about cryo electron microscopy?

Images are captured on film

Scurvy is "a disease caused by a deficiency of vitamin C, characterized by swollen bleeding gums and the opening of previously healed wounds". It arises because the person is unable to make _________ for collagen.

Hydroxyproline

The helices in keratin are α helices.

True

Which of the following diseases can be the result of improper protein folding?

Amyotropic lateral sclerosis (ALS, Lou Gehrig's disease)
Alzheimer's disease
Cancer
Tay-Sachs disease
Scurvy
Sickle cell disease
(All)

α helices spanning a membrane are _________

Hydrophobic

Carbon dioxide is transported in the blood as _________.

bicarbonate

The release of protons from hemoglobin when oxygen binds in the lungs causes _____ carbon dioxide to be produced from bicarbonate

more

The Bohr effect is that hemoglobin _____ ~0.8 protons when oxygen binds.

releases

The more ordered the microcrystalline β-sheets the _________ is the fiber.

Stronger

The globin fold (seen in myoglobin and in hemoglobin) has _________.

mainly α helices

Adding BPG to hemoglobin ______ hemoglobin's affinity for oxygen.

decreases

The drawing below illustrates the fold seen in a ____________ bundle.

4 a-helix

The keratin present in spider's silk is nearly all α-helical.

False (antiparallel B-sheets)

________ are clefts in globular enzymes where substrates and products bind.

Active sites

What is NOT true of collagen?

The triple helix is left-handed.