Abstract
Bacteria are challenged to adapt to environmental variations in order to survive. Under nutritional stress, several bacteria are able to slow down their metabolism into a nonreplicating state and wait for favourable conditions. It is almost universal that bacteria accumulate carbon stores to survive during this nonreplicating state and to fuel rapid proliferation when the growth-limiting stress disappears. Mycobacteria are exceedingly successful in their ability to become dormant under harsh circumstances and to be able to resume growth when conditions are favourable. Rapidly growing mycobacteria accumulate glucosylglycerate under nitrogen-limiting conditions and quickly mobilize it when nitrogen availability is restored. The depletion of intracellular glucosyl-glycerate levels in Mycolicibacterium hassiacum (basonym Mycobacterium hassiacum) was associated with the up-regulation of the gene coding for glucosylglycerate hydrolase (GgH), an enzyme that is able to hydrolyse glucosylglycerate to glycerate and glucose, a source of readily available energy. Highly conserved among unrelated phyla, GgH is likely to be involved in bacterial reactivation following nitrogen starvation, which in addition to other factors driving mycobacterial recovery may also provide an opportunity for therapeutic intervention, especially in the serious infections caused by some emerging opportunistic pathogens of this group, such as Mycobacteroides abscessus (basonym Mycobacterium abscessus). Using a combination of biochemical methods and hybrid structural approaches, the oligomeric organization of M.hassiacum GgH was determined and molecular determinants of its substrate binding and specificity were unveiled.
Highlights
IntroductionThe basic requirements for bacterial growth are not always available
In a changing environment, the basic requirements for bacterial growth are not always available
In order to unveil its molecular mechanism of action, a thorough structural and functional characterization of M. hassiacum GgH (MhGgH) was performed, elucidating its quaternary architecture and providing an atomic detail view of the determinants of substrate specificity, providing new insights into a potentially crucial enzyme underlying the metabolic reactivation of rapidly growing mycobacteria following severe nutrient starvation and expanding the options for therapeutic intervention
Summary
The basic requirements for bacterial growth are not always available. Some of the surviving cells can slow down or suspend their growth to a viable nonreplicating state and persist for months or years (Lewis, 2007). In order to unveil its molecular mechanism of action, a thorough structural and functional characterization of MhGgH was performed, elucidating its quaternary architecture and providing an atomic detail view of the determinants of substrate specificity, providing new insights into a potentially crucial enzyme underlying the metabolic reactivation of rapidly growing mycobacteria following severe nutrient starvation and expanding the options for therapeutic intervention
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