Respiratory Biogenesis during the Cell Cycle of Aerobically Grown Escherichia coli K12. The Accumulation and Ligand Binding of Cytochrome o

Abstract

A quantitative assay is described for the measurement of cytochrome o in intact cells of E. coli. The procedure involves flash protolysis of the CO-liganded, reduced enzyme in the absence of O2 at temperatures (-100.degree. C) at which the rate of recombination of CO is immeasurably slow. Other CO-binding pigments known to be present, particularly cytochrome d, are excluded from the photodissociation spectrum under these conditions. Measurement of the content of cytochrome o in bacteria separated into size (and thus age) classes by zonal centrifugation shows that the cytochrome accumulates continuously probably exponentially, throughout the cell cycle and thus constitutes a constant proportion of cell protein during the cycle. The velocity of recombination of CO with cytochrome o at -65.degree. C is invariant over the cell cycle.