FIG. 1.
Structure and relatedness of coupling proteins from the RP4 and Ti plasmid transfer systems. The length of each protein in amino acid residues is indicated by the numbers at each end. Filled regions indicate amino acid sequences with properties of N-terminal secretion signals. The stippled and cross-hatched regions and their coordinates delimit the two motifs conserved among the members of the TraG family (19, 29). The amino acid substitution mutants of TraGRP4 are indicated by the single-letter designation for the wild-type residue followed by the position number and the mutant residue.