Figure 1.

Identification of the α dimerization domain. Schematic representation of the α protein, redrawn from Ziegelin et al. (19). The localization of the domains and the amino acids substitutions of the α^cr mutations are indicated. The plasmids carry the α fragments, indicated by the amino acid coordinates and by bars, fused to the N-terminal part of the λ CI repressor. The efficiency of plating of λ, λcY17 (immunity sensitive cI mutant; 24) and λ668 (virulent mutant; 25) on the different strains, relative to the control CSH50, is given (for details see Materials and Methods). Closed bars, fragments conferring immunity; open bars, fragments that do not confer immunity.