FIG. 4.

Identification of atypical masses in ribosomal proteins. (A) Deconvoluted electrospray mass spectrum revealed two aberrant signals. Masses of 15,316 Da and 17,474 Da did not match the predicted masses of E. coli ribosomal proteins. (B) Tryptic peptides observed by MALDI-TOF were then used to identify the proteins as ribosomal proteins S6 and S7 (C). The masses of observed and predicted masses are displayed. The protein sequence for each identified protein is indicated, and the covered peptides are underlined.