7RUT

Structure of Human ATP:Cobalamin Adenosyltransferase R190C bound to ATP

Summary for 7RUT

• Entry DOI: 10.2210/pdb7rut/pdb
• Descriptor: Corrinoid adenosyltransferase, MAGNESIUM ION, POTASSIUM ION, ... (6 entities in total)
• Functional Keywords: atp:cobalamin adenosyl transferase, cobalamin, vitamin b12, patient mutation, transferase
• Biological source: Homo sapiens (Human)
• Total number of polymer chains: 6
• Total formula weight: 133783.86

Authors

Mascarenhas, R.,Gouda, H.,Koutmos, M.,Banerjee, R. (deposition date: 2021-08-18, release date: 2021-11-24, Last modification date: 2023-10-18)

Primary citation

Gouda, H.,Mascarenhas, R.,Pillay, S.,Ruetz, M.,Koutmos, M.,Banerjee, R.
Patient mutations in human ATP:cob(I)alamin adenosyltransferase differentially affect its catalytic versus chaperone functions.
J.Biol.Chem., 297:101373-101373, 2021

PubMed Abstract: Human ATP:cob(I)alamin adenosyltransferase (ATR) is a mitochondrial enzyme that catalyzes an adenosyl transfer to cob(I)alamin, synthesizing 5'-deoxyadenosylcobalamin (AdoCbl) or coenzyme B. ATR is also a chaperone that escorts AdoCbl, transferring it to methylmalonyl-CoA mutase, which is important in propionate metabolism. Mutations in ATR lead to methylmalonic aciduria type B, an inborn error of B metabolism. Our previous studies have furnished insights into how ATR protein dynamics influence redox-linked cobalt coordination chemistry, controlling its catalytic versus chaperone functions. In this study, we have characterized three patient mutations at two conserved active site residues in human ATR, R190C/H, and E193K and obtained crystal structures of R190C and E193K variants, which display only subtle structural changes. All three mutations were found to weaken affinities for the cob(II)alamin substrate and the AdoCbl product and increase K. P NMR studies show that binding of the triphosphate product, formed during the adenosylation reaction, is also weakened. However, although the k of this reaction is significantly diminished for the R190C/H mutants, it is comparable with the WT enzyme for the E193K variant, revealing the catalytic importance of Arg-190. Furthermore, although the E193K mutation selectively impairs the chaperone function by promoting product release into solution, its catalytic function might be unaffected at physiological ATP concentrations. In contrast, the R190C/H mutations affect both the catalytic and chaperoning activities of ATR. Because the E193K mutation spares the catalytic activity of ATR, our data suggest that the patients carrying this mutation are more likely to be responsive to cobalamin therapy.

PubMed: 34757128
DOI: 10.1016/j.jbc.2021.101373

Experimental method

X-RAY DIFFRACTION (1.5 Å)