Isolation of a Protein Coded for by the Permease Gene of the Lac Operon of Escherichia coli
The inducible Lac operon of Escherichia coli has been shown to possess three genetic loci: for the enzyme beta-galactosidase, for the enzyme thio-galactoside transacetylase (hereafter referred to as (transacetylase), and for beta-galactoside permease, a membrane transport system [1, 2, 3]. The results of kinetic studies performed on this transport system (as in other examples of biological transport) lead to the postulate that a “carrier” substance is present, this carrier transporting the permeant through the membrane into the cytoplasm. In no case of biological transport thas the kinetic evidence for a carrier been factually substantiated by concomitant isolation of the actual carrier itself, although phospholipids have been tentatively implicated in active Na+ and K + transport in the avian salt gland , a phosphoryl-accepting residue has been identified at ‘the active centre of the membrane-linked Na+, K+ activated ATP-ase system , and both phospholipids and protein have been implicated in monosaccharide transport in the human erythrocyte [6, 7]. The facts that the Lac operon of E. coli is known (to code for only the above three components and that this operon can be induced by gratuitous substrates  bave enabled us to develop techniques with which we lhave identified a cytoplasmic expression of the permease (y+) gene.
KeywordsSalt Gland Membrane Transport System Biological Transport Dashed Line Repre Gratuitous Inducer
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