Chapter 3: 3.3 Beta Sheet Flashcards
Define:
Beta Sheets
Amino acids align themselves in strands which can then form sheets
How are β-sheets formed?
H-bonds create sheetes out of the strands by forming H-bonds between amino acids on adjacent strands
Where do H-bond interactions occur on β-sheets?
Interactions occur between the amino group (N-H) and the carboxyl group (C=O) of the amino acid backbone
Describe:
Side chain orientation in the β-sheets
The side chains project outward and are not involved in sheet formation
Are β-sheets flexible or stretchy?
β-sheets are flexible, not stretchy
In a β-sheet:
On average, how many amino acids particpate in one H-bond?
Each amino acid participates in one H-bond
How can the number of H-bonds in a β-sheet be calculated?
(Number of amino acids per strand)(Number of gaps between strands)
True or False:
β-sheets can be parallel or antiparallel
True
What is the difference between parallel and anti-parallel sheets?
- Parallel sheets: Amino acid chains run in the same direction
- Anti-parallel sheets: Amino acid chains run in opposite directions
Define:
β-turns
180° turns that connect one strand of an anti-parallel β-sheet to the next
Describe:
Structure of β-turns
- Contain 1 hydrogen bond to form the turn
- Involve 4 amino acids, but only 2 of them participate in hydrogen bonding
How do the two types of β-turns differ?
Differ by a 180° rotation of the amino acid in position 2
Which amino acids are very common in β-turns?
Glycine and Proline
Describe:
Type I β-turns
Proline is often in position two as it hold the cis conformation
Describe:
Type II β-turns
Amino acid in position three is almost always Glycine as steric hindrance prohibits any other residue
