"From her office at the Weizmann Institute of Science in Rehovot, Israel, she holds up a blue plastic model of a proteasome, a barrel-shaped structure with a hollow core. The function seems simple: proteins enter the chamber, where they are shredded and then exit as smaller peptide fragments. But the machinery is surprisingly elaborate. The core comprises more than two dozen protein subunits and can associate with a variety of regulatory caps."
"Merbl and her team used mass spectrometry to identify the peptides created by proteasomes in a variety of cells. They then compared the sequences of these peptides to those with known functions, using public databases. Many, they found, matched ones known to obliterate bacteria, such as by piercing their membranes. The team identified other fragments - about 1,000 in total - with sequences that, according to an algorithm, make them likely to be antimicrobial."
Proteasomes are barrel-shaped complexes that degrade proteins into peptide fragments. Mass spectrometry identified many proteasome-generated peptides matching known antimicrobial sequences and about 1,000 additional fragments predicted to be antimicrobial by an algorithm. Computational digestion of all human proteins revealed more than 270,000 possible antimicrobial peptides. Proteasomes can swap regulatory caps during bacterial infection to favour production of bacteria-fighting peptides. Proteasome-mediated peptide generation therefore functions as a widespread innate immune defence, producing diverse antimicrobial fragments from normal cellular proteins capable of targeting and disrupting bacteria.
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