Protein DLA-3 tertiary and quarternary structure

Question 1

What is the tertiary structure of a protein?

Answer 1

The 3-dimensional form of a molecule resulting from distant protein-protein interactions within the same polypeptide chain

Question 2

How are tertiary structure created?

Answer 2

Created when secondary structure fold in on themselves

Question 3

What is the function of side chain interactions of tertiary structures?

Answer 3

Stabilize the tertiary structure

Question 4

What are the functions of globular proteins?

Answer 4

Some kind of dynamic metabolic function

That is a catalytic/regularity/ transport role

Question 5

Describe solubility of globular proteins

Answer 5

Usually good water solubility

-cytosolic dissolved protein

Question 6

Describe the shape and structure of globular proteins

Answer 6

In almost all cases, globular proteins have a different kinds of secondary structure(alpha helix,beta sheet, beta turns)

Relatively spherical in shape (hence globular)

Question 7

Describe proteins designed to function in the plasma membrane

Answer 7

An inside-out protein

Greasy side chains like phenylalanine, isoleucine are pointed outward

Question 8

Explain the tertiary structure of globular polypeptides

Answer 8

Tertiary structure is compact; areas of secondary structure fold to create domains and the final arrangement in protein

Question 9

Describe the location of hydrophobic side chains in water soluble proteins

Answer 9

For water soluble proteins, hydrophobic side chains are buried in the interior

E.x. BCAAs, Phe, Met, are likely to be buried

Question 10

For water soluble proteins, where are hydrophilic side chains likely to be located?

Answer 10

Hydrophilic side chains are likely to be exposed

So Asp, Arg, Lys, Gln, Asn,Ser, Thr(polar and charged) are on the surface

Question 11

Explain the stabilization of the tertiary protein structure

Answer 11

-interactions between side chains of amino acids stabilize tertiary structure

• Amino acids can create areas for intramolecular attractions
  
  • disulfide bonds
  • ions(opposite charges May create a salt bridge)
  • hydrogen bonding
  • dipoles
  • Van deer Waals (London) forces

Question 12

List interactions involved in maintaining tertiary structure

Answer 12

• hydrogen bonds
• Disiulfude binds 2 cysteine -> cystine (-s-s-)
• Electrostatic interactions, ionic, polar interactions
• van deer waals forces
• hydrophobic interactions

Question 13

Explain the importance of the disulfide bond

Answer 13

• disulfide binds May stabilize a protein
• are found in many secreted proteins, but not typically found in cytosolic protein
• disulfide binds are critically important for proper structure of the insulin protein( insulin is secreted

Question 14

How are disulfide bonds formed?

Answer 14

Formed by -SH groups of two cysteine residues -> and a cystine group is formed

-two Cys May be close in the primary structure, or they may be far away

Question 15

Where do hydrophobic interactions occur in tertiary structures?

Answer 15

Between nonpolar side chains of amino acids in interior of protein

E.g. leucine, isoleucine

Question 16

What occurs due to hydrophobic interactions?

Answer 16

Since water cannot associate with these side chains, water molecules attempt to exclude them from the surface of the protein

-same reason oil floats on top of water

Question 17

Briefly state what is the effect and location of hydrogen bonds in tertiary structures

Answer 17

• hydrogen bonds interact between polar side chains

- interactions between polar side chains and water increase the solubility of the protein

Question 18

Give an example of an ionic interaction in tertiary proteins

Answer 18

Interaction of -COO- of Asp with NH3+ of Lys

Question 19

What are Domains?

Answer 19

These are fundamental , functional 3-d structural units of polypeptides caused by folding

Folding within one domain is typically independent of folding within other domains and have their own jobs

Question 20

Give the characteristics of each domain

Answer 20

Each domain has the characteristics of small, compact, globular protein

Question 21

What is the Quatenary structure of protein?

Answer 21

Association of one polypeptide to create a multimeric protein

Question 22

If all the polypeptides in the quatenary structure are the same, What is it called?

Answer 22

Homodimer

Question 23

If some polypeptides in a quaternary structure are different it is a…

Answer 23

Heterodimer

Question 24

2 polypeptides mmaking quaternary structure is called a….

Answer 24

Dimer

Question 25

3 polypeptides making a quatenary structure is called a….

Answer 25

Trimer

Question 26

4 polypeptides making a quatenary structure is called a….

Answer 26

Tetramer

Question 27

How are quatenary structures held together?

Answer 27

By one or more of the following non-covalent interactions:

(Weak attractive forces, but act together)
-hydrogen bonds

• hydrophobic interactions (Van deer Waal forces)
• Electrostatic interactions(ionic and/or polar)
• the disulfide bond is not involved

Question 28

Give two examples of quatenary structure

Answer 28

• Galactose-1- phosphate urydylyltransferase(homodimer)

- hetertrimeric G protein

Question 29

Hemoglobin is an example of …

Answer 29

A tetramer(heterotetramer)

Question 30

What is the importance of a quatenary structure?

Answer 30

• allows for communication between subunits and regulation
• Communication is created when the shape( or conformation ) of one subunit affects a different subunit
• this communication allows regulation (and therefore life)
• this allows for allosteric regulation in enzymes