Fig. 3

Perlustrin alignment and spectra. a Alignment of a nacre protein 70% identical to mature H. laevigata perlustrin isolated from nacre matrix and sequenced on the protein level using automated Edman chemistry [16]. A predicted signal sequence peptide is in red. Sequence regions confirmed by MS/MS-derived peptide sequences are in green. b MS/MS spectrum of a selected sequence-unique peptide of comp70759_c0_seq1_2. This peptide of a mass of 1714.8131 Da was identified with a Posterior Error Probability (PEP) of 5.2e-19 and a mass error of 0.3 ppm. c MS/MS spectrum of a selected sequence-unique peptide of P82595. This peptide showing one miss-cleavage was identified with a PEP of 0.019 and a mass error of 0.3 ppm. Y-ions are shown in red, b-ions are in blue, and fragments with neutral loss are in orange. A few fragment non-standard but advanced annotations with the help of the MaxQuant Expert system [44] are shown in black. For the sake of clarity most advanced annotations are not shown. The mass spectrometer model used, Velos or Elite, is contained in the raw-file name on top of the y-axis of the spectra