The LacY gene is a structural component of the lac operon (lactose operon) system which enables bacteria, such as E. coli, to digest lactose when glucose is scarce. The LacY gene codes for the proteinBeta-galactoside permease. It is a transmembrane symporter found in the cytoplasmic membrane that regulates the transport of lactose into the cell. It does this by pumping Beta-galactosides, including lactose, into the cell in the same direction as the proton gradient. The LacY gene is essential for lactose catabolism.