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 two protein | The first two protein structures to be determined, [[myoglobin]] and [[hemoglobin]], consist 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 (or antiparallel) helices (e.g. bacterial cytochrome c' [[1e83]]). In structures that have beta sheets and alpha helices, one common fold is a single beta sheet that is sandwiched by layers of alpha helices on either side (for example [[Carboxypeptidase A]]). 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 (e.g. [[FIS protein]]) or the zinc finger motif (e.g. engineered zinc finger protein [[2i13]]), feature a short alpha helix that binds to the major groove of DNA. | ||
===Alpha helices in transmembrane proteins=== | ===Alpha helices in transmembrane proteins=== | ||
A common fold found in transmembrane proteins are alpha-helical bundles running from one side to the other side of the membrane. An alpha helix of 19 amino acids (with a length of about 30 angstroms) has the right size to cross the double-layer of a typical membrane. If the helix runs at an angle instead of perfectly perpendicular to the membrane, it has to be a bit longer. There is a write-up on opioid | A common fold found in transmembrane proteins are alpha-helical bundles running from one side to the other side of the membrane. An alpha helix of 19 amino acids (with a length of about 30 angstroms) has the right size to cross the double-layer of a typical membrane. If the helix runs at an angle instead of perfectly perpendicular to the membrane, it has to be a bit longer. There is a write-up on opioid receptors that illustrates this fold in the Molecule of the Month series by David Goodsell (http://pdb101.rcsb.org/motm/217). | ||
===Alpha helices in coiled coils=== | ===Alpha helices in coiled coils=== | ||
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* [[Secondary structure]] | * [[Secondary structure]] | ||
* [[Protein primary, secondary, tertiary and quaternary structure]] / [[Protein primary, secondary, tertiary and quaternary structure (Spanish)|Estructuras primaria, secundaria, terciaria y cuaternaria de las proteínas]] | * [[Protein primary, secondary, tertiary and quaternary structure]] / [[Protein primary, secondary, tertiary and quaternary structure (Spanish)|Estructuras primaria, secundaria, terciaria y cuaternaria de las proteínas]] | ||
* [[Introduction to molecular visualization]] | |||
== References == | == References == | ||
<references/> | <references/> | ||
[[Category:Pages with quizzes]] | [[Category:Pages with quizzes]] | ||