Methionine synthase: Difference between revisions

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The vitamin B12 Cobalamin binding domain has a special characteristic in that, it is most naturally found in a protective conformation to prevent unwanted chemistry from occurring (PDB: 1BMT). This is referred to as a 'capping' mechanism.
The vitamin B12 Cobalamin binding domain has a special characteristic in that, it is most naturally found in a protective conformation to prevent unwanted chemistry from occurring (PDB: 1BMT). This is referred to as a 'capping' mechanism.


In <scene name='90/907471/Bindingdomain1/1'>scene 1</scene>, this is a 3D visual of the the binding domain of Cobalamin, with Cobalt(+1) in pink. Note here, Cobalamin contains a Corrin ring very similar to what we see in heme.
In <scene name='90/907471/Bindingdomain1/1'>scene 1</scene>, this is a 3D visual of the the binding domain of Cobalamin, with Cobalt(+1) in pink. Note here, Cobalamin contains a Corrin ring as seen in heme.


In <scene name='90/907471/Bindingdomain2/1'>scene 2</scene>, we can see where the DMB ligand exists. During its confirmation change, DMB will move away from the Corrin ring and replaced by His 757.
In <scene name='90/907471/Bindingdomain2/1'>scene 2</scene>


In <scene name='90/907471/Bindingdomain3/2'>scene 3</scene>, Cobalt(+1) now accepts a methyl and forming Me-Cob(III)alamin.
In <scene name='90/907471/Bindingdomain3/2'>scene 3</scene>, Cobalt(+1) now accepts a methyl and forming Me-Cob(III)alamin.
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When B12 is not engaged with one of the other three substrate binding domains, it is protected by a <scene name='90/907471/Cap/1'>cap</scene>.
When B12 is not engaged with one of the other three substrate binding domains, it is protected by a <scene name='90/907471/Cap/1'>cap</scene>.


In the Cob(I)alamin binding domain, the <scene name='90/907471/Cap/5'>imidazole side chain containing His 759</scene> replaces the dimethylbenzimidazole (DMB) ligand. His 759 bonds to Asp 757 and Ser 810 via hydrogen bonds to create a ligand triad that increases the efficiency of the methyl transfer during the catalytic cycle (not shown). With His on, the cap is on Cobalamin. When interacting with the activation domain, there is no room for the cap, and the cobalamin moves a bit out of the reach of the histidine (in the crystal structure, they used the His759Gly mutation to favor the His-off conformation).<ref name="Bandarian et al"/>.
In the Cob(I)alamin binding domain, the <scene name='90/907471/Cap/5'>imidazole side chain containing His 759</scene> comes in and out of the B12 domain as the 5th ligand. His 759 bonds to Asp 757 and Ser 810 via hydrogen bonds to create a ligand triad that increases the efficiency of the methyl transfer during the catalytic cycle (not shown). With His on, the cap is on Cobalamin. When interacting with the activation domain, there is no room for the cap, and the Cobalamin moves a bit out of the reach of the Histidine (in the crystal structure, they used the His759Gly mutation to favor the His-off conformation).<ref name="Bandarian et al"/>.


<jmol>
<jmol>
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</StructureSection>
</StructureSection>
== Acknowledgements ==
Many thanks to Dr. Theis, Anna, Mike, and Shaylie for their assistance on creation of 3D images of the B12 domain for MS.
Also thanks to Dr. Drennan for taking the time to review the page and providing very


== References ==
== References ==
Retrieved from "https://proteopedia.org/Methionine_synthase"