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3.2 Sheets

3.2.2 Parallel

The hydrogen bonds in a parallel beta sheet are not perpendicular to the individual strands resulting in component (~1/3 of the peptide dipole) parallel to the strand. The parallel sheet then has an overall macrodipole leaving the an effective charge of ~ +1/15 unit elemental charge at the N-terminus and - 1/15 charge at the C-terminus of each strand of average length (~5 times less than an average alpha helix macrodipole). An example of a mixed beta sheet containing an parallel component is given using the protein thioredoxin (Figure 10 ).

Figure 11. The three-stranded parallel beta sheet in thioredoxin (2TRX.PDB). The three parallel strands are shown in both cartoon format (left) and in stick form containing backbone atoms N, CA, C, and O' (right). Hydrogen bonds are identified by arrows connecting the donor nitrogen and acceptor oxygens. Strands are numbered according to their relative position in the polypeptide sequence.

download 2TRX.PDB

download RasMol script for parallel sheet

No Title - 31 MAY 96
written by Kurt D. Berndt

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