Details

Autor(en) / Beteiligte

• Garcia-Ferrer, Irene
• Arêde, Pedro
• Gómez-Blanco, Josué
• Luque, Daniel
• Duquerroy, Stephane
• Castón, José R.
• Goulas, Theodoros
• Gomis-Rüth, F. Xavier

Titel

Structural and functional insights into Escherichia coli α 2 -macroglobulin endopeptidase snap-trap inhibition

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 2015-07, Vol.112 (27), p.8290-8295

Erscheinungsjahr

2015

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• Significance Proteolytic enzymes are inhibited in vivo by protein inhibitors. Such inhibitors are used by symbiotic bacteria in our gut to protect themselves from digestive peptidases. This is the case for Escherichia coli , which has acquired a large, multidomain inhibitor of broad inhibitory spectrum [ Escherichia coli α 2 -macroglobulin (ECAM)]. We studied ECAM and found it is cleaved by host peptidases, which triggers large conformational rearrangement of the inhibitor—shown by protein crystallography and electron microscopy reconstructions—as well as covalent binding of the peptidase. The latter is blocked similarly to a mouse by a snap trap, which prevents damage to the bacterial envelope. Prey peptidases, however, can still be active in the digestion of intake proteins. The survival of commensal bacteria requires them to evade host peptidases. Gram-negative bacteria from the human gut microbiome encode a relative of the human endopeptidase inhibitor, α 2 -macroglobulin (α 2 M). Escherichia coli α 2 M (ECAM) is a ∼180-kDa multidomain membrane-anchored pan-peptidase inhibitor, which is cleaved by host endopeptidases in an accessible bait region. Structural studies by electron microscopy and crystallography reveal that this cleavage causes major structural rearrangement of more than half the 13-domain structure from a native to a compact induced form. It also exposes a reactive thioester bond, which covalently traps the peptidase. Subsequently, peptidase-laden ECAM is shed from the membrane and may dimerize. Trapped peptidases are still active except against very large substrates, so inhibition potentially prevents damage of large cell envelope components, but not host digestion. Mechanistically, these results document a novel monomeric “snap trap.”