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[Exogenous orthophosphate regulation of ATPase activity of E. coli cells]
Abstract:
The effect of exogenous orthophosphate and mutations in genes, regulating the Pi transport system, on the ATPase activity of E. coli subcellular fractions was studied. It was shown that the orthophosphate starvation resulted in the cessation of the increase in the ATPase activity of membranes and was accompanied by the increase in the analogous activity of a soluble fraction at the expense of the derepression of alkaline phosphatase possessing this activity. The disturbance, resulted from the mutation of protein components participating in the specific binding and transport of orthophosphate, changed the ATPase activity of subcellular fractions: increased the ATPase activity of soluble fraction (independently of the presence of orthophosphate in medium), did not affect significantly the activity of membrane--bound ATPase in the presence of orthophosphate and decreased this activity in the absence of orthophosphate. The data obtained point to the fact that components, binding exogenous orthophosphate and transporting it into a cell, affect the rigidity of the ATPase bound E. coli cytoplasmic membrane. Mutations resulting in the defect in these components relax this bound and lead to the detection of ATPase proper in the periplasm.
Insights
Orthophosphate starvation and transport mutations alter E. coli ATPase activity. Mutations affecting phosphate transport impact membrane rigidity and enzyme localization.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- The regulation of inorganic phosphate (Pi) transport systems is crucial for bacterial homeostasis.
- ATPase activity in Escherichia coli (E. coli) is linked to cellular energy metabolism and transport processes.
- Understanding the interplay between Pi transport and ATPase function provides insights into membrane dynamics.
Purpose of the Study:
- To investigate the impact of exogenous orthophosphate levels and genetic mutations in the Pi transport system on ATPase activity in E. coli subcellular fractions.
- To elucidate the relationship between specific Pi transport proteins and the modulation of ATPase activity in different cellular compartments.
- To determine how defects in orthophosphate binding and transport affect the E. coli cytoplasmic membrane's structural integrity and enzyme localization.
Main Methods:
- Studying ATPase activity in isolated E. coli membrane and soluble fractions under varying orthophosphate conditions.
- Utilizing E. coli mutants with defects in genes regulating the Pi transport system.
- Analyzing the derepression of alkaline phosphatase in response to orthophosphate starvation.
- Assessing the effect of mutations on membrane-bound and soluble ATPase activities in the presence and absence of orthophosphate.
Main Results:
- Orthophosphate starvation led to decreased membrane ATPase activity and increased soluble fraction activity due to alkaline phosphatase derepression.
- Mutations in Pi transport proteins increased soluble fraction ATPase activity irrespective of external orthophosphate.
- These mutations had minimal effect on membrane-bound ATPase activity with orthophosphate but decreased it without.
- Data suggest Pi transport components influence the rigidity of the E. coli cytoplasmic membrane.
Conclusions:
- Components involved in exogenous orthophosphate binding and transport influence the rigidity of the E. coli cytoplasmic membrane.
- Defects in these components relax membrane rigidity, potentially leading to the release of ATPase into the periplasm.
- The study highlights a functional link between inorganic phosphate transport and the structural and enzymatic properties of the E. coli cell envelope.