The Intracellular Concentration of Bound and Unbound Magnesium Ions in Escherichia coli

Charles Hurwitz,Carmen L Rosano

doi:10.1016/s0021-9258(18)95867-9

Charles Hurwitz, Carmen L Rosano

Open Access

https://doi.org/10.1016/s0021-9258(18)95867-9

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Abstract

Abstract The concentration of magnesium ions in solution within Escherichia coli ML 35 was found to be the same as the extracellular concentration over a range of 10-6 m to 10-2 m. Since growth rate was unaffected at 4 x 10-5 m, it was concluded that protein synthesis in vivo is accomplished at much lower concentrations of magnesium than is required for protein synthesis in vitro. Ribosome-bound spermidine, but not putrescine, was found to vary inversely with ribosome-bound magnesium. It is proposed that polyamines, especially spermidine, may be more important for protein synthesis in vivo than is magnesium.

Highlights

Since growth rate was unaffected at 4 X 10M5 M, it was concluded that protein synthesis in vivo is accomplished at much lower concentrations of magnesium than is required for protein synthesis in vitro
It is proposed that polyamines, especially spermidine, may be more important for protein synthesis in vivo than is magnesium
High concentrations of magnesium ions have been shown to be required for various reactions involved in protein synthesis in vitro

Summary

SUMMARY

The concentration of magnesium ions in solution within Escherichia coli ML 35 was found to be the same as the extracellular concentration over a range of 10U6 M to low rd. High concentrations of magnesium ions have been shown to be required for various reactions involved in protein synthesis in vitro. Formation of the polysome complex has been shown to require even higher magnesium concentrations, and optimal conditions for protein synthesis in vitro have been reported to include 1OV M magnesium and 10-l M potassium. Under these conditions, sufficient magnesium is bound to account for 1 cation for every 2 ribosomal phosphate groups [2]. That the stability of ribosomes and other aspects of protein synthesis are strongly influenced by magnesium in vitro is abundantly clear, but the intracellular concentration of free magnesium is unknown. After the supernatant fluids are decanted, the cells are isolated from their original external aqueous environment by cutting off the bottom section of the tube containing the cellular pellet

Intracellular Magnesium

AND METHODS

The disrupted cellular suspension was centrifuged twice at

Findings

In growth medium

DISCUSSION