Spatial colocalization and functional link of purinosomes with mitochondria

Abstract

Purine biosynthetic enzymes organize into dynamic cellular bodies called purinosomes. Little is known about the spatiotemporal control of these structures. Using super-resolution microscopy, we demonstrated that purinosomes colocalized with mitochondria, and these results were supported by isolation of purinosome enzymes with mitochondria. Moreover, the number of purinosome containing cells responded to dysregulation of mitochondrial function and metabolism. To explore the role of intracellular signaling, we performed a kinome screen using a label-free assay and identified that mTOR influenced purinosome assembly. mTOR inhibition disrupted purinosome-mitochondria colocalization and suppressed purinosome formation stimulated by mitochondria dysregulation. Collectively, our data suggests an mTOR-mediated link between purinosomes and mitochondria and suggests a general means by which mTOR regulates nucleotide metabolism by spatiotemporal control over protein association.

Transient protein-protein interactions perturb E. coli metabolome and cause gene dosage toxicity

“…Hence, DHFR is functionally very closely connected to the family of purine/pyrimidine biosynthesis enzymes. Purine biosynthesis enzymes were found to be spatially localized forming the ‘purinosome’, in mammalian cells, but no evidence exists for E. coli (An et al, 2008; French et al, 2016; Deng et al, 2012). It is possible that at basal expression levels DHFR is a member of a dynamic ‘metabolon’ that facilitates channeling of tetrahydrofolate or its derivatives.…”

Physicochemical code for quinary protein interactions in Escherichia coli

“…6 not only add physical−chemical detail to the effects of intracellular crowding (4,12,27,53) but also provide a tool for rational protein surface design. Applications can include optimization of target proteins for in-cell NMR detection (54), surface optimization of protein therapeutics (55), and mutational examination of the yet poorly understood relation between protein motion, spatial localization, and function (7,56,57). The message stands clear and simple to test: Can any protein be tuned to desired rotational motion in E. coli.…”

“…espite considerable progress in mapping out how proteins interact functionally through structure and evolved interfaces (1-3), there is yet little known about how proteins interact nonspecifically upon random diffusive encounters (4)(5)(6)(7)(8)(9)(10). Although these nonspecific "quinary" (11) interactions are typically weak and short-lived, they are still expected to affect function because of their sheer numbers: Under crowded cellular conditions, they compete with specific binding (6)(7)(8), control diffusion (12), and skew structural stability (5,(13)(14)(15)(16)(17)(18)(19).…”

“…Although these nonspecific "quinary" (11) interactions are typically weak and short-lived, they are still expected to affect function because of their sheer numbers: Under crowded cellular conditions, they compete with specific binding (6)(7)(8), control diffusion (12), and skew structural stability (5,(13)(14)(15)(16)(17)(18)(19). The question is then to what extent this dynamic background of nonspecific interactions is biologically controlled and optimized.…”

A New View into the Regulation of Purine Metabolism: The Purinosome

“…In addition to the colocalization with microtubules, purinosomes were found to colocalize with mitochondria through application of super-resolution fluorescence microscopy [61]. Figure 3A-B shows the colocalization of purinosomes with mitochondria.…”