Sandbox Reserved 641: Difference between revisions
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== '''Structure''' == | == '''Structure''' == | ||
Glutamate Dehydrogenase is a hexamer that is comprised of two trimer subunits. These two subunits are stacked on top of each other and composed of three domains. The top of each domain contains a "NAD-binding domain" that has the conserved nucleotide-binding motif. A larger helix-loop-helix structure rises above this and is referred to as an "antenna." This antenna contains approximately 50 amino acids and is thought to play a major role in regulation of the enzyme. This antennae structure is only found in animals. The bottom domain contacts a domain in the other trimer, holding the two trimers together. | Glutamate Dehydrogenase is a hexamer that is comprised of two trimer subunits. These two subunits are stacked on top of each other and composed of three domains. The top of each domain contains a "NAD-binding domain" that has the conserved nucleotide-binding motif. A larger helix-loop-helix structure rises above this and is referred to as an "antenna." This antenna contains approximately 50 amino acids and is thought to play a major role in regulation of the enzyme. This antennae structure is only found in animals. The bottom domain contacts a domain in the other trimer, holding the two trimers together. The total size of each of the subunits is approximately 56.1 kD and 506 amino acids long. | ||
When a substrate binds to the enzyme it binds to the deep recess of the cleft between the NAD binding domain and the lower domain. Along the outside surface of the cleft a coenzyme binds causing the binding domain to rotate by about 18 degrees and close down on the substrate and coenzyme. As the cleft is closing the antenna pushes against the pivot helix of the adjacent subunit. The pivot helix rotates counter clockwise around both the helical axis and the trimer 3-fold axis. The hexamer then compresses the inner core showing that catalysis involves the entire hexamer. | When a substrate binds to the enzyme it binds to the deep recess of the cleft between the NAD binding domain and the lower domain. Along the outside surface of the cleft a coenzyme binds causing the binding domain to rotate by about 18 degrees and close down on the substrate and coenzyme. As the cleft is closing the antenna pushes against the pivot helix of the adjacent subunit. The pivot helix rotates counter clockwise around both the helical axis and the trimer 3-fold axis. The hexamer then compresses the inner core showing that catalysis involves the entire hexamer. | ||
