Fibrous Protein

Question 1

Which amino acid is called secondary amino acid, why?

Answer 1

Proline because it forms a cyclic ring

Question 2

Why do fibrous proteins have low solubility in water

Answer 2

Because they play a structural integrity role in tissue/create barriers

Question 3

3 most common fibrous proteins

Answer 3

Collagen, elastin and keratin

Question 4

Which is the most abundant protein in the body

Answer 4

Collagen (present in all tissues and organs)

Question 5

Function of collagen

Answer 5

Provides framework that gives the tissue their form and structural strength

Question 6

Collagen characteristics of following organ/tissue

1. Tendons
2. Bone
3. Skin
4. Cornea

~these are all what type of collagen

Answer 6

1. Bundled in tight parallel fibers that provide great strength
2. Fibers arranged at angle to each other to resist mechanical shear (meshwork)
3. Loosely woven, flexible fibers
4. Nearly crystalline; transparent

~Type I collagen meaning they form fibrils (in tissues that run long distances)

Question 7

Collagen that forms sheets would be

Answer 7

Network forming (forms mesh to work as a barrier)

Question 8

Function of fibril-associated collagen (FACTs)

Answer 8

Attach two different collagen fibers

Question 9

Structure of collagen

What keeps it tight

Answer 9

Triple helix (braided)

Hydrogen bond which is added by hydroxylation, without this it would become loose (like a braid without a hair tie)

Question 10

Amino acid sequence of collagen

Answer 10

Gly-X-Y

X= usually proline
Y= often hydroxyproline or hydroxylysine
~needs glycine because it is the smallest AA

Question 11

1. Hydroxyproline involved in

2. Hydroxylysine is site of

Answer 11

1. Hydrogen bond formation to stabilize the triple helix

2. Site of attachment of carbohydrate moieties (usually glucose and galactose)

Question 12

Synthesis of collagen:

What is necessary to start synthesis of a pro-alpha-chain

Answer 12

Signal sequence (acts as GPS) - directs growing polypeptide chain into cisternae of rER
~signal sequence is cleaved in ER to yield pro-alpha-chain

Question 13

Synthesis of collagen:

Without signal sequence what would happen

Answer 13

Protein will be translated but will be present outside of the lumen (needs to be inside to continue process)

Question 14

Synthesis of collagen:
What happens in the rER

This process requires what 3 things

What two enzymes catalyze this reaction

Answer 14

Post-translational hydroxylation of proline and lysine

Molecular oxygen, vitamin C (ascorbic acid), and ferrous iron

Prolyl and lysyl hydroxylase

Question 15

What has to happen in order for collagen to form triple helix

Answer 15

Collagen has to be hydroxylated

Question 16

Vitamin C deficiency leads to?

Symptoms

Answer 16

Scurvy (bleeding gums and bleeding joints)

~need vitamin c for prolyl and lysyl hydroxylase

Question 17

Synthesis of collagen:

What happens to hydroxylysine residues?

Answer 17

They need to be modified by glycosylation with glucose or galactose

Question 18

Synthesis of collagen
For pro alpha chains to form procollagen what needs to happen

How does the winding of triple helix happen (what direction)

Answer 18

Carboxy terminal end folds and forms disulfide bonds

From carboxyl to amino terminus

Question 19

Synthesis of collagen

The completed triple helix goes to where

Answer 19

Golgi apparatus to be secreted out of cell via secretory vesicles

Question 20

Synthesis of collagen
What happens when the triple helix leaves the cell

What happens if this does not happen

~this step happens where in the cell

Answer 20

N and C procollagen peptidases remove the terminal propeptides to release the triple helix tropocollagen molecule

Collagen will be soluble in water

~ECM (not within the cell)

Question 21

Synthesis of collagen

How are the collagen fibrils formed

Answer 21

Individual tropocollagen molecules associate together

Question 22

Synthesis of collagen
What enzyme matures the collagen fibers

What does it do

Answer 22

Lysyl oxidase

Forms cross links (makes it stronger)

~this also happens outside of cell

Question 23

Function of collagenase

Answer 23

Cleave intact collagen fibers into smaller fragments for degradation in lysosome so that old collagen can be replaced by new collagen

Question 24

Ehlers Danlos Syndrome

1. Symptoms
2. Deficient in?
3. What else can lead to this syndrome?

Answer 24

1. Stretchy skin and hyper-extendible joints (contortionists)
2. Lysylhydroxylase, procollagen peptidases (collagen processing enzymes)(cannot form cross links)
3. Replacement of glycine with another amino acids (rare)

Question 25

Osteogenesis imperfecta

1. AKA
2. Caused by
3. Other symptoms

Answer 25

1. Brittle bone syndrome
2. Glycine replaced
3. Retarded wound healing, humpback spine, blue scleras, bones break easily

Question 26

Main difference between collagen and elastin

Answer 26

Their function; synthesis is similar

Question 27

Function of elastin

Where is elastin found in the body

Answer 27

Gives tissues and organs ability to stretch without tearing

Lungs, walls of large blood vessels, elastic ligaments, and skin

Question 28

1. Elastin forms desmosine which results in
2. Formed from ?
3. What enzyme is required for this process

Answer 28

1. Extensively interconnected, rubbery network (gives elastin its elastic properties)
2. Formed from 3 allysines and 1 lysine
3. Lysyloxidase

Question 29

Elastin is degraded by?

Where is this enzyme mostly found

Function

Answer 29

Elastase

WBCs (specifically neutrophils)

Main function is neutrophils will release elastase to degrade debris in lung tissue

Question 30

Alpha 1-antitrypsin

1. What does it inhibit
2. Deficiency in this will lead to
3. What is required to bind this to target proteases?
4. Main function

Answer 30

1. Proteolytic enzymes that hydrolyze and destroy proteins
2. Emphysema
3. Alpha 1-AT methionine
4. Protects lung alveoli from damage from elastase

Question 31

Lysyloxidase is __ containing

Answer 31

Copper

Question 32

A 30 year old woman presents with progressive dyspnea. She denies smoking, her fmhx reveals that her sister has similar problems. Which etiology explains the patients symptoms?

Answer 32

Defect in alpha 1 antitrypsin