Coiled coil: Difference between revisions
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A coiled-coil or superhelix is formed by coiling two, three or four α-helices together. The helical strands are held together by the hydrophobic force formed between nonpolar side chains from the | A '''coiled-coil''' or '''superhelix''' is formed by coiling two, three or four α-helices together. The helical strands are held together by the hydrophobic force formed between nonpolar side chains from the | ||
different peptide strands. A <b>heptad repeat</b> pattern of short chain hydrophobic residues in the primary structure consistently bring these nonpolar side chains | different peptide strands. A <b>heptad repeat</b> pattern of short chain hydrophobic residues in the primary structure consistently bring these nonpolar side chains | ||
together every seventh residue. These nonpolar residues from different strands are properly located to interact with one another because the helix is slightly distorted by being less tightly wound than the normal α-helix so that it has a pitch of 0.51 instead of 0.54 and there | together every seventh residue. These nonpolar residues from different strands are properly located to interact with one another because the helix is slightly distorted by being less tightly wound than the normal α-helix so that it has a pitch of 0.51 instead of 0.54 and there | ||
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== Additional Illustrations == | == Additional Illustrations == | ||
<Structure load='1UO2' size='500' frame='true' align='right' caption='' scene='Coiled_coil/Gcn4/1' /> | <Structure load='1UO2' size='500' frame='true' align='right' caption='Coiled-cil from GCN4 (PDB code [[1uo2]])' scene='Coiled_coil/Gcn4/1' /> | ||
Two strands of general control protein GCN4 from baker's yeast. Observe the slight coil in the strands. (<scene name='Coiled_coil/Gcn4/1'>Initial scene</scene>) Every seventh residue, <scene name='Coiled_coil/Gcn4_2/1'>shown in spacefill</scene>, is nonpolar, and with 3.5 residues per turn each heptad repeat is aligned with the one below and above it, as well as being in position to interact with the heptad repeat on a second strand. Looking down the <scene name='Coiled_coil/Gcn4_3/1'>spline</scene> of the contact. The <scene name='Coiled_coil/Gcn4_4/1'>side chains</scene> of the residues located between the heptad repeats spiral around the helix away from the side chains on the partner strand, thus not permitting interactions between these side chains of the two strands. | Two strands of general control protein GCN4 from baker's yeast. Observe the slight coil in the strands. (<scene name='Coiled_coil/Gcn4/1'>Initial scene</scene>) Every seventh residue, <scene name='Coiled_coil/Gcn4_2/1'>shown in spacefill</scene>, is nonpolar, and with 3.5 residues per turn each heptad repeat is aligned with the one below and above it, as well as being in position to interact with the heptad repeat on a second strand. Looking down the <scene name='Coiled_coil/Gcn4_3/1'>spline</scene> of the contact. The <scene name='Coiled_coil/Gcn4_4/1'>side chains</scene> of the residues located between the heptad repeats spiral around the helix away from the side chains on the partner strand, thus not permitting interactions between these side chains of the two strands. | ||
