**Protein Symmetry
**

Java version

HTML 5 version (does not require Java; downloads and moves
slowly)

**I. Introduction**

Proteins of the C_{2}, C_{4}, D_{2}, and D_{4} symmetry
point groups are below with operations of the characteristic
symmetry elements of the point groups. The subunits of the
proteins are color coded so the change in orientation is clearly
observed.

**cyclic** (C_{n}) - contain one single C_{n}
rotation axis. In this point group note that the
n in C_{n} is equal to the number of monomers and the angle of
rotation is 360^{o}/n..

**dihedral** (D_{n}) - These have mutually
perpendicular rotation axes. Specifically they contain at least 1 C_{2}
axis perpendicular to a C_{n} axis (Canter and Schimmel.
Biophysical Chemistry - Part 1). The minimal number of
subunits is n. Most protein oligomers fall into this
category.

Click
on the symmetry element button below to see each individual
protein undergo the symmetry operation and compare the rotated
protein on the left to the fixed orientation on the right.

Note: The Jmol command used to carry
out the rotations also rotate the axes. We are working to
fix this problem so the superpositions can be better visualized.

For more information see
Biochemistry Online: Chapter 5C -
Model Binding Systems

**II. General Structure**

C2 Symmetry: Alcohol Dehydrogenase

Rotational Axis

*Rotate protein 180 degrees about Y-axis

C4 Symmetry: Neuraminidase

C4 Rotational Axis

*Rotate protein 90 degrees about Y-axis

D2 Symmetry: Phosphofructokinase

C2 Rotational Axis

*Rotate protein 180 degrees about Y-axis

D4 Symmetry: Glycolate Oxidase

C4 Rotational Axis

*Rotate protein 90 degrees about Y-axis

Horizontal Plane

*Rotate protein 90 degrees about Z-axis to see mirror
image subunits above and below Z-axis (plane is perpendicular to Y-axis)