Alpha helix: Difference between revisions
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==Types of proteins and folds that contain alpha helices== | ==Types of proteins and folds that contain alpha helices== | ||
===Alpha helices in soluble (globular) proteins=== | ===Alpha helices in soluble (globular) proteins=== | ||
The first protein structure to be determined, myoglobin, consists mainly of alpha helices. Researchers were surprised to see how random the orientation of helices seemed to be. Other all alpha-helical proteins show bundles of nearly parallel helices. In structures that have a mixture of beta sheets with alpha helices, a single beta sheet is often sandwiched by layers of alpha helices on either side, although many other folds have been observed. When an alpha helix runs along the surface of the protein, one side of it will show polar side chains (solvent accessible) while the other side will show non-polar side chains (part of the hydrophobic core). | |||
The alpha helix fits nicely into the major groove of DNA. Many common DNA-binding motifs, such as the helix-turn-helix or the zinc finger motif, feature a short alpha helix that binds to the major groove of DNA. | |||
===Alpha helices in transmembrane proteins=== | ===Alpha helices in transmembrane proteins=== | ||
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===Alpha helices in coiled coils=== | ===Alpha helices in coiled coils=== | ||
Alpha helices are named after alpha keratin, a fibrous protein consisting of two alpha helices twisted around each other in a coiled-coil (see [[Coiled coil]]). In leucine zipper proteins (such as [[Gcn4]]), the ends of the two alpha helices bind to two opposite major grooves of DNA. The name leucine zipper comes from the regularly spaced leucine side chains from both helices that form the hydrophobic core of these structures. The structure of collagen, the most abundant human protein, is also a coiled coil of helices, but it is not made up of alpha helices. | |||
[[Coiled coil]] | |||
[[Gcn4]] | |||
==Experimental evidence== | ==Experimental evidence== | ||