Fig. 6.

pI shift around start codons. The distribution of pI values of the 20 N-terminal residues excluding the initial Met (solid line) and the 20 residues of the spurious ORF extension (broken line) that precedes the start codon is plotted for Halobacterium. Transmembrane proteins and proteins with a signal sequence or twin-arginine export motif have been excluded from the analysis. The small inset shows the correlation of the pI value of the N-terminal region of the protein (pI-post, plotted on the x-axis) and the pI value of the spurious ORF extension (pI_pre, plotted on the y-axis). The majority of the N-terminal regions are acidic, while a large fraction of the spurious extensions is highly alkaline