Existence of a molecular ruler in proteasomes suggested by analysis of degradation products

Abstract
Analysis of the degradation products from two proteins, the insulin B‐chain and human hemoglobin, generated by archaebacterial Thermoplasma acidophilum 20 S proteasomes, revealed an unexpectedly broad specificity. In spite of the vast number of different peptides found, they fell into a rather narrow size range. This suggests that a molecular ruler exists which determines the length of the cleavage products.