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![[Figure 9]](mh5163fig9mag.jpg)
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Figure 9
Proposed mechanism for the putative secondary THF binding at the interface between the two N-terminal domains in zebrafish FDH. The tetrameric FDH, with correctly oriented C-terminal NADP+-dependent dehydrogenase domains (blue) and N-terminal hydrolase domains (cyan), converts the formyl group of 10-formyl-THF into CO2 and generates THF. An intermediate domain between the N- and C-terminal domains is shown as a black line. The substrate (10-FTHF) and product (THF) are shown as yellow and pink spheres, respectively. Each Nt-FDH domain initially accommodates one substrate for catalysis to generate the product THF at the active site. THF subsequently accumulates in the proximity of the binding site as the reaction continues. The increased THF promotes the dimerization of Nt-FDH by binding to the interface between the two adjacent Nt-FDH domains, yielding an additional THF binding site. The presence of SHMT, which uses THF as its substrate, removes THF from FDH and hence eliminates product inhibition. |
![[Figure 9]](mh5163fig9.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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