malB region in Escherichia coli K 12: characterization of new mutations

Abstract

Phenotypic characterization and mapping of more than 50 Mal- mutations located in the malB region lead one to divide the site for Mal-λs mutations (formerly called gene malB) in that region, into 2 adjacent genetic segments malJ and malK. MalJ and malK are both involved in maltose permeation. It is suggested that (i) malK and lamB, the only known gene specifically involved in phage λ adsorption, constitute an operon of polarity malK lamB, (ii) malJ and malK correspond to 2 different genes, and (iii) a promoter for the malK lamB operon is located between malJ and malK. Since λ receptors and maltose permease are inducible by maltose and absent in malT mutants, it is likely that the expression of the malK lamB operon is controlled by the product of gene malT, the positive regulatory gene of the maltose system.