Figure 4.

Digestion pattern of oxidized insulin B chain by purified 20S proteasomes from non-infected and infected cells. About 10 μg substrate was digested with 1 μg proteasomes for 24 hr at 37°. Digestion mixtures were fractionated by HPLC, and absorbance peaks were analysed by MALDI-TOF or electrospray ion trap mass spectrometry. Thick, medium and thin lines correspond to peptides recovered at >4%, 1–4% and <1% yield of the total digest, respectively. Only peptides recovered with ≥0·2% yield are indicated. Thick, medium and thin arrows indicate cleavage sites that generated peptides with total yields >5%, 1–5% and <1% of the total digest, respectively. Peptides labelled with asterisks were found with an amount less than the 0·2% of the total of digest, but were included because in the counterpart they were recovered at ≥0·2%.