Biogenesis of a bacterial metabolosome for propanediol utilization

Abstract

Bacterial metabolosomes are a family of protein organelles in bacteria. Elucidating how thousands of proteins self-assemble to form functional metabolosomes is essential for understanding their significance in cellular metabolism and pathogenesis. Here we investigate the de novo biogenesis of propanediol-utilization (Pdu) metabolosomes and characterize the roles of the key constituents in generation and intracellular positioning of functional metabolosomes. Our results demonstrate that the Pdu metabolosome undertakes both “Shell first” and “Cargo first” assembly pathways, unlike the β-carboxysome structural analog which only involves the “Cargo first” strategy. Shell and cargo assemblies occur independently at the cell poles. The internal cargo core is formed through the ordered assembly of multiple enzyme complexes, and exhibits liquid-like properties within the metabolosome architecture. Our findings provide mechanistic insight into the molecular principles driving bacterial metabolosome assembly and expand our understanding of liquid-like organelle biogenesis.

In Vitro Analysis of Bacterial Microcompartments and Shell Protein Superstructures by Confocal Microscopy

“…51 We speculate that a liquid-liquid phase separation (LLPS) mechanism is likely to apply to the early stages of metabolosome assembly, as supported by recent reports focusing on the Pdu BMC. 52 This has also been suggested for both α- and β-carboxysomes too, supporting the notion that LLPS may be a common mechanism for BMC biogenesis. 53, 54 Our data does not support the shell or shell protein structures themselves being liquid.…”

Inferring assembly-curving trends of bacterial micro-compartment shell hexamers from crystal structure arrangements

“…The presence of less organized/compact encapsulated contents in other BMC types, when compared to hexadecameric RuBisCO 8 , and the observation of compartment formation in the absence of cognate cargo 9, 10 , pointed to the existence of other assembly pathways for other BMC types. In line with this, a recent study on Pdu BMC biogenesis proved that cargo-first and shell-first assembly pathways are both feasible, even when cargo-enzymes coalesce following a hierarchical organization mode 11 .…”

“…elongatus PCC 7942, the presence of pre-organized cargo preceding shell assembly 7 . A similar study on Pdu Sent compartments pointed instead to a less synchronized mechanism, with coexistence of cargo-first and shell-first events 11 . A similar model could operate with -carboxysomes, as indicate the gathering of CsoS2 scaffolding protein to portion of shells, which would precede recruitment of RuBisCO and final BMC closure 35 , or the multiple layers of RuBisCO attached to the inner surface of partial -carboxysome shells 8,36 .…”

Construction of Osmotic Pressure Responsive Vacuole-like Bacterial Organelles with Capsular Polysaccharides as Building Blocks

“…The development of artificial organelles or subcellular compartments to endow novel functions, regulate gene expression, or explore the biogenesis mechanism of subcellular structures is always one of the focused areas of synthetic biology. − From the perspective of biotechnology, the application of subcellular compartments not only enhances the rate and fidelity of biochemical reactions by concentrating enzymes and substrates − but also sequesters toxic metabolic products to mitigate interference with cellular metabolism. − To this end, many bacterial microcompartments, − elastin-like polypeptides-based compartments, , lumazine synthases-based compartments, or protein crystalline inclusions have been developed.…”