A SIGNAL TRANSDUCER FOR AEROTAXIS IN ESCHERICHIA-COLI

The newly discovered aer locus of Escherichia coli encodes a 506-resid ue protein with an N terminus that resembles the NifL aerosensor and a C terminus that resembles the flagellar signaling domain of methyl-ac cepting chemoreceptors. Deletion mutants lacking a functional Aer prot ein failed to congregate around air bubbles or follow oxygen gradients in soft agar plates. Membranes with overexpressed Aer protein also co ntained high levels of noncovalently associated flavin adenine dinucle otide (FAD), We propose that Aer is a flavoprotein that mediates posit ive aerotactic responses in E. coli. Aer may use its FAD prosthetic gr oup as a cellular redox sensor to monitor environmental oxygen levels.