Fig. 2.

Relative frequency of N-terminal methionine cleavage for each of the 19 possible amino acids in the +2 position. Frequencies are calculated as the number of observed cleavage events for the amino acid divided by the sum of the observed cleaved and uncleaved termini with that amino acid in the +2 position [cleaved/(cleaved + uncleaved)]. Numbers above the bars are the total number of observed termini with this amino acid in the +2 position for uncleaved or +1 position for cleaved proteins. The amino acid code “Z” represents either Leu or Ile, which are indistinguishable in the technology used. In general the trends agree with research published on the phenomenon in other organisms, with cleavage occurring in the presence of small amino acids in the +2 position.