The amino acid sequence of beta-galactosidase of the Lactose Operon of Escherichia coli will be determined by methods of protein chemistry. Beta-Galactosidase polypeptides produced by mutant strains of bacteria are being isolated to aid sequence work and to extend gene-protein relationships. Complementation of beta-galactosidase fragments is being investigated. The primary structure of thiogalactoside transacetylase will also be determined. BIBLIOGRAPHIC REFERENCES: Zabin, I. and A.V. Fowler: Beta-Galactosidase, the Lactose Permease Protein and Thiogalactoside Transacetylase, Chapter in Molecular Aspects of Operon Control, J. H. Miller and W.S. Reznikoff, Eds., Cold Spring Harbor Laboratory, New York (1977), in press. Langley, K.E., and I. Zabin: Beta-Galactosidase alpha-Complementation: Properties of the Complemented Enzyme and Mechanism of the Complementation Reaction, Biochemistry (1976), in press.