Nonsense Mutations in the Maltose A Region of the Genetic Map of Escherichia coli

Abstract

The isolation of one amber mutation in malQ , one ochre mutation in malP , and seven amber mutations in malT is reported. A study of their phenotypic expressions in the presence of the amber suppressor su III and the ochre suppressor su c suggests that (i) malQ is the structural gene for amylomaltase; (ii) malQ and the structural gene for maltodextrin phosphorylase, malP , belong to the same operon; (iii) the malT product, which promotes the expression of the malP-malQ operon, is a protein synthesized in limiting amounts by the wild-type strain.