User:Eric Martz/5eon: Difference between revisions
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The <scene name='73/733958/Hexamer_of_5eon/5'>surface of the fiber</scene> is mostly charged <font color="blue">'''Lys+'''</font> and <font color="red">'''Glu-'''</font> sidechains, with an occasional Trp or Gln, interspersed with Ala (spheres). | The <scene name='73/733958/Hexamer_of_5eon/5'>surface of the fiber</scene> is mostly charged <font color="blue">'''Lys+'''</font> and <font color="red">'''Glu-'''</font> sidechains, with an occasional Trp or Gln, interspersed with Ala (spheres). | ||
The | ==Charges== | ||
The peptides were designed to form salt bridges between chains in the hexamer, assuming the peptides are parallel in the hexamer. Surprisingly, the peptides are anti-parallel in the hexmer that formed. This precluded salt bridges within the hexamer. The authors note that this shows that the energetics of the hydrophobic core are dominant, with the salt bridges being unnecessary. | |||
==Sequence== | The charges form <scene name='73/733958/Hexamer_of_5eon/2'>helices of opposite charge</scene> on the surface, reminiscent of [[User:Ke Xiao/Geobacter pilus models|Xiao's theoretical model of the ''Geobacter sulfurreducens'' pilus]]. Terminal charges on the chains were blocked (see below). Unlike Xiao's model, none of these form salt bridges (a few opposite charges are water-bridged). | ||
[[Cation-pi interactions]] involving Phe cannot form since Phe is buried and Lys is on the surface. A few cation-pi interactions may form between Trp on the surface and Lys. | |||
==Salt Bridges Between Hexamers== | |||
The arrangement of rows of alternating negative and positive charge on the surfaces of the hexamers suggests that salt bridges might form between hexamers, stabilizing the protein crystal. In fact, there is | |||
only one salt bridge | |||
between each pair of hexamers, as shown in the crystallographic unit cell. | |||
==Sequence and Blocked Termini== | |||
The peptide sequence is constructed from 4 copies of heptad | The peptide sequence is constructed from 4 copies of heptad | ||