LacI Homotetramer

3D Structure of LacI Homotetramer with Ligand

CPK Color Scheme C O N P

On this page, you can see four identical LacI proteins (green, blue, red, white) bound to each other. This tutorial will highlight some of this repressor's structure and thus function. You can click and drag to see the shape before clicking on the buttons below.

Convert the proteins to cartoon shape and zoom in on the portions that allow the four LacI monomers to hold on to each other to make the homotetramer.

Reposition the LacI tetramer and highlight the ligand bound to each monomer. The ligand is a modified form of lactose and is shown in CPK colors. Why are these LacI molecules not bound to DNA at this time?

Get rid of 3 LacI proteins and focus on just one. You will see one ligand floating outside the visible LacI to remind you what is inside the LacI protein.

Slab into this one LacI monomer to see the lactose-like ligand in its binding site inside LacI.

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