Oxygen binding to myoglobin induces a conformational change. We will explore this transition in the next slide.
Backbone trace for deoxymyoglobin. to animate the superposition of oxymyoglobin. Feel free to move the model during display of the trace.
allows you to see how the position of the residues differs with the conformational change. We can also between the two models.
The largest change in the tertiary structure produced by oxygenation is translation of the F helix by about 1 Å.
F helices in deoxymyoglobin and oxymyoglobin.
Two questions arise naturally: How does binding of oxygen to the heme Fe cause the F helix to slide along the heme group? What is the link between this very small change in tertiary structure and the cooperative binding of O2 in hemoglobin?
To answer the first question let's consider just the E and F helices, together with part of the G helix.
Now between the oxy and deoxy conformations. The F helix in oxy conformation is shown in magenta. Note the movement of the proximal His side chain relative to its position in the deoxy conformation. Click to overlay the two conformations.
To understand how oxygen binding tiggers translation of the F helix, we need to find out why the proximal histidine, His F8, moves.