A 44-Year-Old Man Is Evaluated Due to Progressive Dyspnea Over

question 131

Multiple Choice

A 44-year-old man is evaluated due to progressive dyspnea over the past several years.  The patient has no associated chest pain or palpitations.  Physical examination shows a prolonged expiratory phase without wheezes or rhonchi.  CT scan of the chest demonstrates bilateral lower lobe-predominant emphysema.  Further testing reveals that the patient has a protease inhibitor deficiency, which has led to increased elastin fiber breakdown.  Elastin fibers within alveolar walls normally allow the lung to stretch during active inspiration and recoil during passive expiration.  Which of the following most likely contributes to this property of elastin?

• A)Abundant interchain disulfide bridges
• B)Chain assembly to form a triple helix
• C)Heavy post-translational hydroxylation
• D)High content of polar amino acids
• E)Interchain cross-links involving lysine