Multiple Choice
Suppose a cell membrane is 45 Å thick & an embedded protein has 7 parallel transmembrane α-helical segments. Calculate the minimum # of aa-residues required for all 7 α-helical segments to traverse the membrane.
2
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4. Protein Structure
Alpha Helix Pitch and Rise
Multiple Choice
How many amino acid residues are needed for the α-helix backbone to obtain exactly one full periodic repeat?
A
1.5
B
3.6
C
5.4
D
18
Verified step by step guidance1
Understand the structure of an α-helix: It is a common secondary structure in proteins, characterized by a right-handed coil where each turn of the helix contains approximately 3.6 amino acid residues.
Identify the periodic repeat of an α-helix: A full periodic repeat of an α-helix is defined as one complete turn of the helix, which corresponds to 3.6 amino acid residues.
Calculate the length of one full periodic repeat: The length of one full periodic repeat in an α-helix is approximately 5.4 Å (angstroms), which is the distance covered by one complete turn.
Determine the number of residues for a specific length: To find out how many residues are needed for a specific length of the α-helix, divide the desired length by the length per residue (1.5 Å per residue).
Calculate the number of residues for 5.4 Å: Divide 5.4 Å by 1.5 Å per residue to find the number of residues needed for one full periodic repeat of the α-helix.
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