cb6b00523_si_001.pdf (11.77 MB)
Direct Evidence for Metabolon Formation and Substrate Channeling in Recombinant TCA Cycle Enzymes
journal contribution
posted on 2016-08-24, 00:00 authored by Beyza Bulutoglu, Kristen E. Garcia, Fei Wu, Shelley D. Minteer, Scott BantaSupramolecular assembly of enzymes
into metabolon structures is thought to enable efficient transport
of reactants between active sites via substrate channeling.
Recombinant versions of porcine citrate synthase (CS), mitochondrial
malate dehydrogenase (mMDH), and aconitase (Aco) were found to adopt
a homogeneous native-like metabolon structure in vitro. Site-directed mutagenesis performed on highly conserved arginine
residues located in the positively charged channel connecting mMDH
and CS active sites led to the identification of CS(R65A) which retained
high catalytic efficiency. Substrate channeling between the CS mutant
and mMDH was severely impaired and the overall channeling probability
decreased from 0.99 to 0.023. This work provides direct mechanistic
evidence for the channeling of reaction intermediates, and disruption
of this interaction would have important implications on the control
of flux in central carbon metabolism.