lamB is the structural gene for the lambda receptor, an oligomeric outer membrane protein from Escherichia coli K12 involved in phage lambda adsorption. We show that, under certain conditions, in a strain diploid for gene lamB, all the missense lamB mutations conferring lambda resistance that we have tested are dominant with respect to wild-type. We propose a model which allows a quantitative interpretation of the data. It is based on negative complementation at the level of oligomerisation. Wild-type and mutant subunits would assemble at random forming homo- and hetero-oligomers. Only wild-type homo-oligomers would be efficient for phage inactivation. For some classes of missense mutations the hetero-oligomers would have the capacity to bind, but not to inactivate the phage. The model confirms that active lambda receptor is a trimer and implies that for this secreted protein there is no preferential assembly of subunits originating from the same polysome.
Negative dominance in gene lamB: random assembly of secreted subunits issued from different polysomes. Publishing Authors By Initials
