6r2b
Crystal structure of the SucA domain of Mycobacterium smegmatis KGD after soaking with succinylphosphonate
Structural highlights
FunctionKGD_MYCS2 Shows three enzymatic activities that share a first common step, the attack of thiamine-PP on 2-oxoglutarate (alpha-ketoglutarate, KG), leading to the formation of an enamine-thiamine-PP intermediate upon decarboxylation. Thus, displays KGD activity, catalyzing the decarboxylation from five-carbon 2-oxoglutarate to four-carbon succinate semialdehyde (SSA). Also catalyzes C-C bond formation between the activated aldehyde formed after decarboxylation of alpha-ketoglutarate and the carbonyl of glyoxylate (GLX), to yield 2-hydroxy-3-oxoadipate (HOA), which spontaneously decarboxylates to form 5-hydroxylevulinate (HLA). And is also a component of the 2-oxoglutarate dehydrogenase (ODH) complex, that catalyzes the overall conversion of 2-oxoglutarate to succinyl-CoA and CO(2). The KG decarboxylase and KG dehydrogenase reactions provide two alternative, tightly regulated, pathways connecting the oxidative and reductive branches of the TCA cycle.[1] [2] Publication Abstract from PubMedMycobacterial KGD, the thiamine diphosphate (ThDP)-dependent E1o component of the 2-oxoglutarate dehydrogenase complex (OGDHC), is known to undergo significant conformational changes during catalysis with two distinct conformational states, previously named as the early and late state. In this work, we employ two phosphonate analogues of 2-oxoglutarate (OG), i.e. succinyl phosphonate (SP) and phosphono ethyl succinyl phosphonate (PESP), as tools to isolate the first catalytic steps and understand the significance of conformational transitions for the enzyme regulation. The kinetics showed a more efficient inhibition of mycobacterial E1o by SP (Ki 0.043+/-0.013mM) than PESP (Ki 0.88+/-0.28mM), consistent with the different circular dichroism spectra of the corresponding complexes. PESP allowed us to get crystallographic snapshots of the Michaelis-like complex, the first one for 2-oxo acid dehydrogenases, followed by the covalent adduction of the inhibitor to ThDP, mimicking the pre-decarboxylation complex. In addition, covalent ThDP-phosphonate complexes obtained with both compounds by co-crystallization were in the late conformational state, probably corresponding to slowly dissociating enzyme-inhibitor complexes. We discuss the relevance of these findings in terms of regulatory features of the mycobacterial E1o enzymes, and in the perspective of developing tools for species-specific metabolic regulation. Conformational transitions in the active site of mycobacterial 2-oxoglutarate dehydrogenase upon binding phosphonate analogues of 2-oxoglutarate: From a Michaelis-like complex to ThDP adducts.,Wagner T, Boyko A, Alzari PM, Bunik VI, Bellinzoni M J Struct Biol. 2019 Nov 1;208(2):182-190. doi: 10.1016/j.jsb.2019.08.012. Epub, 2019 Aug 30. PMID:31476368[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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