Conformational Changes in Lactate Dehydrogenase
| Binding and dissociation can be explained by the structural changes that take place upon the binding of either NAD+ or NADH. One such pronounced structural change is the large movement of the protein loop between two of the beta-strands. Arg 101 interacts with the pyrophosphate of NAD+ or NADH, and can be found on the middle of this loop. When no coenzyme is bound the loop and Arg 101 will be extended out into the solvent. However, when the coenzyme binds to the enzyme the loop swings down to cover the coenzyme, excluded water, and perhaps most importantly force the nicotinamide ring of the coenzyme deep into the active site pocket. In the picture to the left you can see what the enzyme looks like in the unbound state. Notice how Arg 101(green) sticks out away from the enzyme. |
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Now in this picture to the right you can see the enzyme in its bound state. Notice how Arg 101(green) cover the coenzyme(red). This is significant in that it holds the coenzyme in place while forcing it deep into the active site.You can also note some of the overall conformational changes that have taken place in the overall enzyme. |
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