Updated: 7/27/2019

Elastin

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Questions
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Evidence
6
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Topic
Overview
  •  Structure  
    • rich in proline, lysine, glycine
      • unlike collagen, can exist in nonglycosylated forms
    • fibrillin protein binds to tropoelastin to form elastic fibers  
      • Marfan's disease is caused by a defect in fibrillin 
        • presentation
          • long extremities including fingers
          • scoliosis
          • myopia and lens dislocations
            • upward (like a martian leaving for outer space)
              • as opposed to a downward dislocation in homocystinuria
          • mitral valve prolapse
          • ↑ for aortic aneurism
  • Function
    • is an elastic protein
      • found in tissues where stretch is needed
        • lungs, dermis of the skin, large arteries, elastic ligaments, vocal cords, ligamenta flava of vertebrae
        • desmosine interchain cross linking between lysine residues gives the protein its elastic stretch
    • degraded by elastase
      • α1-antitrypsin normally inhibits elastase
        • class of protease inhibitors
        • synthesized in the liver
      • excess elastase activity caused by α1-antitrypsin (AAT) deficiency
        • absent α1-globulin peak in serum protein electrophoresis
        • autosomal codominant inheritence
        • presentation
          • panacinar emphysema
            • worsened by smoking
            • early onset
              • smoking without AAT deficiency usually causes centriacinar emphysema
          • cirrhosis
Clinical Significance

Disease 

Comments

Marfan syndrome

  • Almost exclusively AD
  • Mutation in FBN gene
    • encodes fibrillin-1 gene on chromosome 15
  • Patients are susceptible to aortic disease, MVP, lens dislocation, scoliosis, pectus deformity, arachnodactyly

α1-antitrypsin deficiency

  • Autosomal codominant inheritence
  • α1-antitrypsin inhibits elastase
  • Can lead to panacinar emphysema and hepatic disease
 
   

Marfan’s syndrome

 

α1-antitrypsin deficiency

 

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(M1.BC.14.32) A 26-year-old tall, thin woman is seen in the office. On exam you note upward dislocation of her lens as well as findings shown in Figure A. Cardiac auscultation reveals a mid-systolic click followed by a systolic murmur loudest at the apex. Which of the following describes the protein likely to be defective in this woman? Tested Concept

QID: 100097
FIGURES:
1

Forms makeup of bone, skin, and tendons

28%

(88/316)

2

Lies in the actin groove

2%

(6/316)

3

Binds tropoelastin

43%

(135/316)

4

Made of polymerized dimers of tubulin

11%

(35/316)

5

Formed of repetitive Gly-Pro-X sequences

16%

(49/316)

M 1 E

Select Answer to see Preferred Response

(M1.BC.13.17) Which of the following factors gives the elastin molecule the ability to stretch and recoil? Tested Concept

QID: 100082
1

Hydroxylation of proline and lysine rich regions

17%

(30/181)

2

Cross-links between lysine residues

49%

(88/181)

3

Elastase activity

14%

(25/181)

4

Triple helix formation

14%

(25/181)

5

Cleavage of disulfide rich terminal regions

4%

(8/181)

M 1 D

Select Answer to see Preferred Response

Evidence (6)
EXPERT COMMENTS (10)
Private Note