Figure 3.

Positive ion mode electrospray mass spectrum of the refolded, full-length, mature AprA. The major peak in the spectrum (49 500 Da) corresponds exactly to the recombinant protein without the initiator methionine. The peak at 49 534 Da may represent a calcium adduct. The peak at 49 632 Da corresponds to AprA retaining the N-terminal methionine.