2Fo − Fc (white) and Fo − Fc (green) electron-density maps for three residues where heterogeneity is observed by crystallography and mass spectrometry. All 2Fo − Fc maps are contoured at 1 × r.m.s. values. (a) Residue 12 is Pro in Lili-Mip 1 and Thr in Lili-Mip 2. The difference map (green) is at the 3σ level. (b) Residue 39 is Val in Lili-Mip 1 and Phe in Lili-Mip 2. The difference map (green) is at the 2σ level in the first panel to show the complete ring of Phe. (c) Residue 50 is Asn in Lili-Mip 1 and Thr in Lili-Mip 2. The difference map (green) is contoured at the 3σ level. In all three figures, panel 1 shows the additional densities after refining only the Lili-Mip 1 sequence (residues in yellow) and panel 2 after refining only the Lili-Mip 2 sequence (residues in orange). Panel 3 shows that after refining with both Lili-Mip 1 and 2 sequences, no additional densities are observed. The electron-density map depicted is using data from PDB entry 4nyq.