Structural elements of cyanobacterial co-factor-independent phosphoglycerate mutase that mediate regulation by PirC

• DOI: 10.1128/mbio.03378-24
• Publication Date: 2025-04-04T10:35:43Z
• Authors: Tim Orthwein; Janette T. Alford; Nathalie Sofie Be...; Phillipp Fink; Karl Forchhammer
• Keywords: Polyhydroxybutyrate; Phosphoglycerate mutase; Thermostability; Synechocystis

The 2,3-bisphosphoglycerate-independent phosphoglycerate mutase (iPGAM) has been identified as a regulating key point in the carbon storage metabolism of cyanobacteria. Upon nitrogen starvation, iPGAM is inhibited by PII-interacting regulator PirC, which released from its interaction partner PII due to elevated 2-oxoglutarate levels. In silico analysis 338 different iPGAMs revealed deep-rooted distinctive evolution Remarkably, cyanobacterial possess unique loop structure and an extended C-terminus. Our mass photometry suggests that forms complex with three individual PirC monomers. Biolayer interferometry PirC-iPGAM affected C-terminal structural elements iPGAM. A C-terminally truncated enzyme showed loss control twofold increased enzymatic activity compared iPGAM-WT (wild type), demonstrated assays. By contrast, deleting significantly reduced this variant. Physiological experiments were carried out variant strains Synechocystis, these deleted. strain expressing similar overproduction polyhydroxybutyrate deletion PirC. However, contrast latter, higher overall biomass accumulation, making them better chassis for production or other valuable substances than PirC-deficient mutant.IMPORTANCEThe primordial cyanobacteria responsible developing oxygenic photosynthesis early evolution. pathways fixed allocation, co-factor-independent plays crucial role directing first CO2 fixation product, 3-phosphoglycerate, toward central anabolic glycolytic-derived pathways. This work reveals distinct within photosynthetic organisms. We have two specific segments affect through interactor protein understanding allowed us engineer altered fluxes. Since can directly convert into products, our results demonstrate novel approach biotechnical use.