Beta sheet
The β sheet is a commonly occurring form of regular secondary structure in proteins, first proposed by Linus Pauling and Robert Corey in 1951. It consists of
two or more amino acid sequences within the same protein that are arranged
adjacently and in parallel, but with alternating orientation such that hydrogen
bonds can form between the two strands. The amino acid chain is almost fully
extended throughout a β strand. The N-H groups
in the backbone of one strand establish hydrogen bonds with the C=O groups in the backbone of
the adjacent, parallel strand(s). The cumulative effect of multiple
such hydrogen bonds arranged in this way contributes to the sheet's
stability and structural rigidity and integrity. The α-C atoms of
adjacent strands stand 3.5Å apart.
The side chains from the amino acid residues found in a β sheet
structure may also be arranged such that many of the adjacent
sidechains on one side of the sheet are hydrophobic, while many of
those adjacent to each other on the alternate side of the sheet are
polar or charged (hydrophilic).
Some sequences involved in a β sheet, when traced along the
backbone, take a hairpin turn in orientation (direction),
sometimes through one or more prolines.
- See also : tertiary structure -- α helix -- collagen helix
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