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Publication Abstract from PubMed

Clostridium thermocellum is a potential microbial platform to convert abundant plant biomass to biofuels and other renewable chemicals. It efficiently degrades lignocellulosic biomass using a surface displayed cellulosome, a megadalton sized multienzyme containing complex. The enzymatic composition and architecture of the cellulosome is controlled by several transmembrane biomass-sensing RsgI-type anti-sigma factors. Recent studies suggest that these factors transduce signals from the cell surface via a conserved RsgI extracellular (CRE) domain (also called a periplasmic domain) that undergoes autoproteolysis through an incompletely understood mechanism. Here we report the structure of the autoproteolyzed CRE domain from the C. thermocellum RsgI9 anti-sigma factor, revealing that the cleaved fragments forming this domain associate to form a stable alpha/beta/alpha sandwich fold. Based on AlphaFold2 modeling, molecular dynamics simulations, and tandem mass spectrometry, we propose that a conserved Asn-Pro bond in RsgI9 autoproteolyzes via a succinimide intermediate whose formation is promoted by a conserved hydrogen bond network holding the scissile peptide bond in a strained conformation. As other RsgI anti-sigma factors share sequence homology to RsgI9, they likely autoproteolyze through a similar mechanism.

Insight into the autoproteolysis mechanism of the RsgI9 anti-sigma factor from Clostridium thermocellum.,Takayesu A, Mahoney BJ, Goring AK, Jessup T, Ogorzalek Loo RR, Loo JA, Clubb RT Proteins. 2024 Apr 10. doi: 10.1002/prot.26690. PMID:38597224^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.