Protein Symmetry

Java version

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

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I. Introduction

Proteins of the C₂, C₄, D₂, and D₄ 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 C₂ 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

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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)