| Structure | ||||||||||||||||||||||||||||||||
| Mitochondrial malate dehydrogenase (mMDH) functions as a dimer in solution in a "head-to-head" packing arrangment. It is structurally and funtionally simular to other dehydrogenases. While structurally similar to cytoplasmic malate dehydrogenase (cMDH) and lactate dehdrogenase (LDH), small but significant differences have been found in the polar versus nonpolar accessible surface areas. Another notable difference is cMDH and LDH are found as tetramers in solution.
Three helices and their counterparts form the interface between the subunits. |
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| Malate dehydrogenase as a dimer, with citrate. | ||||||||||||||||||||||||||||||||
| Rotation off/on | ||||||||||||||||||||||||||||||||
| Citrate | ||||||||||||||||||||||||||||||||
| Ball and stick/ Cartoon | ||||||||||||||||||||||||||||||||
| Helices/Sheets only | ||||||||||||||||||||||||||||||||
| Each subunit contains 314 amino acids with its own independent allosterically regulated active site.
Three beta-sheets are formed from the 11 beta-strands in the subunit. The beta strands are located in the interior of the molecule with only the turns being exposed to the solvent. The amino-terminal coenzyme-binding domain is made up of the first six beta-stands which run parallel to each other and are connected by alpha helical segments to form the first beta-sheet. Two antiparallel beta-stands with a right handed twist, which are connected by a three residue hairpin turn, make up the second beta sheet. Found between the first two sheets, the third sheet contains two antiparallel strands that twist and interacts with a third antiparallel stand. There are nine alpha-helices in the subunit. Three are involved in dimerization. The rest are located on the exterior and hence exposed to the solvent. Three long helices have distinct bends in them caused by a disruption in a helical H-bond and is mediated instead by a water bond. |
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| Malate dehydrogenase as a dimer, with malate and NAD | ||||||||||||||||||||||||||||||||
| Malate | ||||||||||||||||||||||||||||||||
| NAD | ||||||||||||||||||||||||||||||||
| Rotation off/on | ||||||||||||||||||||||||||||||||
| Ball and stick/ Cartoon | ||||||||||||||||||||||||||||||||
| Helices/Sheets only | ||||||||||||||||||||||||||||||||
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