Protein DLA- Secondary Structure Flashcards

1
Q

Describe the secondary structure of proteins

A

Secondary structure can be created when there is a regular (or repeating) series of binding arrangements

For proteins, this regular arrangement is the peptide bond which links amino acid together

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2
Q

Protein secondary structure include:

A
  • helical structures
  • beta structure(maximally extended primary sequence)
  • Beta bend(or turn)
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3
Q

What causes the formation of secondary structures?

A

Result from local arrangement of adjacent amino acids into an organized 3-dimensional structure

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4
Q

What is the function of hydrogen bond within secondary structure?

A

The hydrogen bonds that stabilize the secondary structure are formed between the atoms that compose the peptide bonds

-hydrogen bonding is repetitive because peptide bonding is repetitive

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5
Q

What type of helix do proteins have and why?

A

All amino acids in nature have an L-configuration and so form a left handed helix

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6
Q

Differentiate between inter- and intra-

A

Intra- interactions WITHIN the same molecule

Inter- interactions between different molecules

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7
Q

Explain where intrachain hydrogen bonds located in secondary protein structures

A

Intrachain hydrigen bonding located in the alpha-helix between the carbonyl oxygen from one amino acid is H-bonded to an alpha nitrogen of the 4th distant amino acid in the polymer

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8
Q

Briefly describe the alpha-helix structure

A
  • Has 3.6 residues per turn

- R groups extended outward

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9
Q

What may disrupt an alpha helix?

A
  1. Proline
  2. Maybe glycine to a lesser extent
  3. Charge repulsion: many charged amino acids that are all found on the same side, or adjacent to each other
  4. Many amino acids with bulky R groups that are next to each other on the helix
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10
Q

Why does proline disrupt an alpha helix?

A

Since it’s side chain forms a bond from the R group to alpha nitrogen, it causes a kink in the alpha helix that breaks it

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11
Q

Why does glycine disrupt an alpha helix?

A

Since it’s R group is so small, it’s not well tolerated in the alpha helix

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12
Q

Describe the characteristics of the helical wheel of the alpha helix

A
  • shows how amino acid side chains are directed to the outside
    • May lead to constraints on the structure
    • dependent on primary structure
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13
Q

How many different globular proteins are there?

A

Millions(infinite)

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14
Q

What is the purpose of the “globin fold” in myoglobin?

A

The “globin fold” for myoglobin is designed to hold a porphyrin ring which has an iron atom in its center

Useful for reversible oxygen binding

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15
Q

Detail the unique structure of myoglobin

A
  • predominantly alpha helix(lacks beta sheet)

- myoglobin also has some turns and bends and some unorganized structure

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16
Q

What does myo- mean?

17
Q

Describe the B-sheet

A
  • Or the beta- pleated sheet
  • All of the atoms of the peptide bond are involved in hydrogen bonding
  • strands visualized as broad arrows
  • the beta sheet may be parallel or anti-parallel
18
Q

Differentiate parallel and anti-parallel B-sheet

A

Anti- parallel= N-terminus goes in one direction and then turns around

Parallel= two strands going in the same direction

19
Q

Parallel beta-pleated sheet has…

A

Alternating side chains

20
Q

Where do hydrogen bonds occur in beta pleated sheets?

A

Between adjacent amino acids in carboxy oxygen and amino nitrogen.

21
Q

Give an example of a protein that predominantly beta-pleated sheet

A

Silk is just about 100% beta sheet

Silk protein is bundled into fibers, spun into thread and then woven to create cloth/fabric

22
Q

What is the function of the B-bend?

A

To reverse the direction of the polypeptide

-Can link alpha helixes/beta sheets to others(infinite combinations

23
Q

Describe the structure of the B-bend.

A
  • often include charged residues
  • stabilized by ionic and/or H-bonds
  • made of a few amino acids
24
Q

What are seupersecondary structures?

A

-result from local folding of secondary structures into small, discrete, “commonly-observed aggregates” of secondary structures

25
Give 4 examples of super secondary structures
- B-a-B unit - Green key - B- meander - B-barrel
26
Give 2 examples of extended super secondary structures
- twisted B sheet | - B-barrel
27
Give three examples of fibrous proteins
- silk - collagen - keratin
28
Describe keratin as a fibrous protein and location
Keratin- combination of alpha helix and beta sheet In hair, nails, horn
29
Describe the collagen as a fibrous protein and it’s location
Collagen- in skin, tendon, bone Most abundant protein in mammals
30
Describe silk as a fibrous protein
In spiders, caterpillars, all. Beta sheet
31
Give the general characteristics of fibrous proteins
- has one dominating secondary structure - a long rod like structure - low(or none) water solubility - a structural role
32
Why is Collagen structure so special?
- it does not have an alpha-helix or beta -pleated sheet | - instead has the collagen triple helix
33
Why must the collagen triple helix be so tight?
Helix must be very tight, so where each helix contacts the other, amino acids with very small side chains are present(glycine, alanine)
34
Why can collagen structure be described as repetitive?
Every third amino acid is glycine
35
What amino acids are in a beta bend? How many residues make up a beta bend?
- beta bends are made up of proline and glycine | - beta bends are made up of 4 amino acid residues