The 503-nm Pigment of Escherichia coli B: Characterization and Nutritional Conditions Affecting Its Accumulation

Abstract

Escherichia coli B was shown to contain a pigment with a single symmetrical absorption band at 503 nm, which cannot be attributed to a cytochrome. The absorption of tetrahydroporphyrin in vitro closely resembled that of P-503 in intact cells. The compounds which rendered P-503 colorless, such as cyanide, azide, hydrazine, thiocyanate, hydroxylamine, dithionite, sulfite, and methylcyanide, also rendered tetrahydroporphyrin colorless. The pigment was present when the cells were grown aerobically or anaerobically in glucose minimal medium, or aerobically in either lactate or succinate minimal medium, but the pigment was not found in cells grown in complex media or in minimal media supplemented with methionine. A model is presented to suggest the involvement of methionine in the conversion of coproporphyrinogen to protoporphyrin. A variety of evidence suggesting that the 503-nm chromophore is in kinetic equilibrium with flavoprotein is discussed. However, it is not a participant in main line respiration, as its rate of reduction upon exhaustion of oxygen was too slow, and the rate of respiration in resting-cell suspensions was independent of P-503 concentration.

The respiratory chains of Escherichia coli.

“…The 503-nm Pigment Under certain growth conditions, a pigment absorbing at about 503 nm can be observed in reduced-minus-oxidized spectra of E. coli cells. Such conditions include growth aerobically in minimal media with glucose, lactate, or succinate as carbon source or anaerobically with glucose (356) and under iron-limited conditions (Hubbard et al, unpublished data). The absence of this pigment in complex media may be due to its repression by amino acids (348, 356).…”

“…ATP is required for association of heme with apocytochrome o. 415 pigment is bleached by cyanide, azide, hydrazine, and dithionite and does not react with CO (356). These authors suggested that the compound was coprotetrahydroporphyrin and, although in kinetic equilibrium with flavoprotein, did not participate in the major electron flux of the respiratory chain.…”

The biology of Zymomonas.

“…A pigment absorbing at 503 nm has been detected in different spectra of yeast and several bacteria (74,99). This pigment is not a hemoprotein; it displays the same properties as tetrahydroporphyrin (95,124). Kropinski et al (93) detected this pigment in Zymomonas ATCC 10988; judging from their data, there is not very much present.…”

“…The eventual role of this pigment in the metabolism of Zymomonas is not clear. In E. coli this pigment may have some function in electron transport, because it is in kinetic equilibrium with flavoprotein (124).…”

Oxygen-limited continuous culture and respiratory energy conservation in Escherichia coli

“…Determination of cytochrome content. The cytochrome content of cells was estimated by difference spectrophotometry (29). Dithionite-reduced versus oxidized difference spectra were employed to detect and quantitate cytochromes d, b1, and a,.…”