Helix bundle

Source: Wikipedia, the free encyclopedia.

A helix bundle is a small

fold composed of several alpha helices
that are usually nearly parallel or antiparallel to each other.

Three-helix bundles

villin as expressed in chickens
(PDB ID 1QQV).

Three-helix bundles are among the smallest and fastest known cooperatively folding structural domains.

villin headpiece domain is only 36 amino acids long and is a common subject of study in molecular dynamics simulations because its microsecond-scale folding time is within the timescales accessible to simulation.[2][3] The 40-residue HIV accessory protein has a very similar fold and has also been the subject of extensive study.[4] There is no general sequence motif associated with three-helix bundles, so they cannot necessarily be predicted from sequence alone. Three-helix bundles often occur in actin-binding proteins and in DNA-binding proteins
.

Four-helix bundles

Four-helix bundles typically consist of four helices packed in a

The specific topology of the helices is dependent on the protein – helices that are adjacent in sequence are often

human growth hormone, cytokine,[5] and Lac repressor C-terminal. The four-helix bundle fold has proven an attractive target for de novo protein design, with numerous de novo four-helix bundle proteins having been successfully designed by rational[6] and by combinatorial[7]
methods. Although sequence is not conserved among four-helix bundles, sequence patterns tend to mirror those of coiled-coil structures in which every fourth and seventh residue is hydrophobic.

See also

  • Knobs into holes packing

References

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  2. .
  3. .
  4. .
  5. ^ a b Branden C, Tooze J. (1999). Introduction to Protein Structure 2nd ed. Garland Publishing: New York, NY.
  6. PMID 3043666
    .
  7. .

External links