Figure 4.

An oligoclonal family of Sec clones has been selected for changes to acidic residues. The numbers adjacent to lines connecting clones are the number of mutations shared (and unique mutations when ending the lineage) and numbers in parenthesis enumerate acquired acidic residues. Shaded circles represent theoretical intermediates. The bold circle reflects the most common member of the family. Hypervariable region 4 (HV4) is modeled to be in a similar position as in T cell receptors (29).