P51 amino acid sequence variations. Amino acids different from N. risticii Illinois, including insertions and deletions are divided by the number of sequences plotted for each amino acid position (# aa diffs). The horizontal axis displays P51 amino acid positions (aa position) including the signal peptide and all detected amino acid insertions (515 aa total). SP, signal peptide. E, external loop; and TM, transmembrane domain are based on the predicted secondary structure . The number of sequences available at each amino acid position on P51 (# seqs) is shown below.