Biology subjects

Lee, J. K. J.

Publications and source records attributed to Lee, J. K. J..

2 recordsLinked to original sources

bioRxiv2022

CryoEM Reveals Oligomeric Isomers of a Multienzyme Complex and Assembly Mechanics

Propionyl-CoA carboxylase (PCC) is a multienzyme complex consisting of up to six -subunits and six {beta}-subunits. Belonging to a metabolic pathway converging on the citric acid cycle, it is present in most forms of life and irregularities in its assembly lead to serious illness in humans, known as propionic acidemia. Here, we report the cryogenic electron microscopy (cryoEM) structures and assembly of different oligomeric isomers of endogenous PCC from the parasitic protozoan Leishmania tarentolae (LtPCC). These structures and their statistical distribution reveal the mechanics of PCC assembly and disassembly at equilibrium. We show that, in solution, endogenous LtPCC {beta}-subunits form stable homohexamers, to which different numbers of -subunits attach. Sorting LtPCC particles into seven classes (i.e., oligomeric formulas 0{beta}6, 1{beta}6, 2{beta}6, 3{beta}6, 4{beta}6, 5{beta}6, 6{beta}6) enables formulation of a model for PCC assembly. Our results suggest how multimerization regulates PCC enzymatic activity and showcase the utility of cryoEM in revealing the statistical mechanics of reaction pathways.

biophysics↗

bioRxiv2022

Discovery, Structure, and Function of Filamentous 3-Methylcrotonyl-CoA Carboxylase

3-methylcrotonyl-CoA carboxylase (MCC) is a biotin-dependent enzyme necessary for leucine catabolism in most organisms. While the crystal structure of recombinant bacterial MCC has been characterized, the structure and potential polymerization of native MCC remain elusive. Here, we discovered that native MCC from Leishmania tarentolae (LtMCC) forms filaments and determined its structure at near-atomic resolution using cryoEM. 6{beta}6 LtMCC dodecamers assemble in a twisted-stacks architecture, manifesting as supramolecular rods extending up to approximately 400 nanometers. LtMCCs in filaments bind biotin but are not covalently biotinylated and lack coenzyme A. Filaments elongate by stacking 6{beta}6 LtMCCs onto the exterior -trimer of the terminal 6{beta}6 dodecamer. This stacking immobilizes the biotin carboxylase domains, sequestering the enzyme in an inactive state within the mitochondrial matrix. Our results support a new model for LtMCC catalysis, termed the dual-swinging-domains model, and cast new light on the functional significance of polymerization in the carboxylase superfamily and beyond.

molecular biology↗