Dominant secondary structure element in myoglobin and hemoglobin: which motif predominates?
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Aβ-strand (beta strand)
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Bα-helix (alpha helix)
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CReverse turn (β-turn)
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DAll of these equally
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ECollagen-like triple helix
Answer
Correct Answer: α-helix (alpha helix)
Explanation
Introduction:Protein secondary structure comprises repeating motifs like α-helices and β-sheets. Globins (myoglobin and hemoglobin) are classic α-helical proteins.
Given Data / Assumptions:
- Considering globin fold proteins.
- Myoglobin and hemoglobin share a conserved fold composed largely of helices A–H.
Concept / Approach:
The globin fold is dominated by α-helices connected by short loops; β-structure is minimal to absent.
Step-by-Step Solution:
1) Identify structural class: all-α proteins.2) Count elements: 7–8 helices per subunit, loops connect helices, negligible β-strand content.3) Conclude α-helix predominance.Verification / Alternative check:
Crystal structures and secondary-structure assignments (e.g., DSSP) show majority α-helix content in globins.
Why Other Options Are Wrong:
β-strands and β-turns are present in many proteins but not dominant in globins; “All equally” is incorrect; collagen triple helix is not present in globins.
Common Pitfalls:
Assuming all proteins contain balanced α and β content.
Final Answer:
α-helix (alpha helix)