Abstract
The phosphotransferase system (PTS) is involved in the use of carbon sources in bacteria. Bacillus sphaericus, a bacterium with the ability to produce insecticidal proteins, is unable to use hexoses and pentoses as the sole carbon source, but it has ptsHI genes encoding the two general proteins of the PTS: enzyme I (EI) and the histidine phosphocarrier (HPr). In this work, we describe the biophysical and structural properties of HPr from B. sphaericus, HPrbs, and its affinity towards EI of other species to find out whether there is inter-species binding. Conversely to what happens to other members of the HPr family, HPrbs forms several self-associated species. The conformational stability of the protein is low, and it unfolds irreversibly during heating. The protein binds to the N-terminal domain of EI from Streptomyces coelicolor, EINsc, with a higher affinity than that of the natural partner of EINsc, HPrsc. Modelling of the complex between EINsc and HPrbs suggests that binding occurs similarly to that observed in other HPr species. We discuss the functional implications of the oligomeric states of HPrbs for the glycolytic activity of B. sphaericus, as well as a strategy to inhibit binding between HPrsc and EINsc.
Highlights
The bacterial phosphoenolpyruvate (PEP): sugar phosphotransferase system (PTS) regulates the use of carbon sources in bacteria
The basic composition of the PTS is similar in all species described so far; it is formed by a cascade of phosphoryl-transfer steps from PEP to the sugar-specific enzyme II permeases (EIIs)
In the first step of the PTS, EI is phosphorylated by PEP at the active-site histidine; subsequently, the phosphoryl group is transferred to histidine phosphocarrier (HPr), at its active-site histidine [2,5,6]; HPr transfers the phosphate to the active site of an EII permease
Summary
The bacterial phosphoenolpyruvate (PEP): sugar phosphotransferase system (PTS) regulates the use of carbon sources in bacteria. It is involved in: (i) cell movement towards carbon sources (chemotaxis); (ii) transport and uptake of several carbohydrates through the cell wall; and, (iii) regulation of several metabolic pathways in both gram-negative and gram-positive bacteria [1,2,3,4]. The basic composition of the PTS is similar in all species described so far; it is formed by a cascade of phosphoryl-transfer steps from PEP to the sugar-specific enzyme II permeases (EIIs). In low-G+C gram-positive bacteria, and a few gram-negative organisms, HPr can be phosphorylated by an ATP-dependent kinase on a serine residue
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