Luo Hong, Hong Sung-Yong, Sgambelluri R Michael, Angelos Evan, Li Xuan, Walton Jonathan D
Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
Chem Biol. 2014 Dec 18;21(12):1610-7. doi: 10.1016/j.chembiol.2014.10.015. Epub 2014 Dec 4.
Amatoxins are ribosomally encoded and posttranslationally modified peptides that account for the majority of fatal mushroom poisonings of humans. A representative amatoxin is the bicyclic octapeptide α-amanitin, formed via head-to-tail macrocyclization, which is ribosomally biosynthesized as a 35-amino acid propeptide in Amanita bisporigera and in the distantly related mushroom Galerina marginata. Although members of the prolyl oligopeptidase (POP) family of serine proteases have been proposed to play a role in α-amanitin posttranslational processing, the exact mechanistic details are not known. Here, we show that a specific POP (GmPOPB) is required for toxin maturation in G. marginata. Recombinant GmPOPB catalyzed two nonprocessive reactions: hydrolysis at an internal Pro to release the C-terminal 25-mer from the 35-mer propeptide and transpeptidation at the second Pro to produce the cyclic octamer. On the other hand, we show that GmPOPA, the putative housekeeping POP of G. marginata, behaves like a conventional POP.
鹅膏毒素是核糖体编码且经翻译后修饰的肽，占人类致命蘑菇中毒事件的大部分。一种典型的鹅膏毒素是双环八肽α-鹅膏菌素，它通过首尾大环化形成，在双孢鹅膏和远亲蘑菇环带盔孢伞中作为一种35个氨基酸的前体肽经核糖体生物合成。尽管丝氨酸蛋白酶的脯氨酰寡肽酶（POP）家族成员被认为在α-鹅膏菌素的翻译后加工中起作用，但确切的机制细节尚不清楚。在这里，我们表明环带盔孢伞中的毒素成熟需要一种特定的POP（GmPOPB）。重组GmPOPB催化两个非加工性反应：在内部脯氨酸处水解，从35个氨基酸的前体肽释放C端25肽，以及在第二个脯氨酸处进行转肽反应以产生环状八聚体。另一方面，我们表明环带盔孢伞假定的管家型POP GmPOPA表现得像一种传统的POP。
