Mutants (ompA) Affecting a Major Outer Membrane Protein of Escherichia coli K12

Abstract

Independent mutants (70) were analyzed affecting a major protein, polypeptide II*, of the outer cell envelope membrane from E. coli K12. They were classified as nonsense mutants of the amber type (20%), mutants most likely of the missense type possessing the protein at normal concentrations (9%), and mutants missing the protein or harboring it at much reduced concentrations for unknown reasons (71%). Of the mutants 40 were analyzed genetically and all mapped at or near ompA, the structural gene for protein II*. Two-dimensional electrophoretic analyses of envelopes from such mutants revealed an unusual heterogeneity of the protein which on such patterns appeared as at least 12 well separated spots, and the majority of these is due to artifacts of the method but apparently specific for this protein. In no case was a polypeptide fragment found in envelopes from the nonsense mutants. The results are discussed regarding 2 different phages [Tu II and K3] which use the protein as a receptor and concerning the biosynthetic incorporation of the protein into the outer membrane.