In vitro reconstitution of sortase-catalyzed pilus polymerization reveals structural elements involved in pilin cross-linking

Chungyu Chang, Brendan R. Amer, Jerzy Osipiuk, Scott A. McConnell, I. Hsiu Huang, Van Hsieh, Janine Fu, Hong H. Nguyen, John Muroski, Erika Flores, Rachel R.Ogorzalek Loo, Joseph A. Loo, John A. Putkey, Andrzej Joachimiak, Asis Das, Robert T. Clubb, Hung Ton-That

研究成果: Article同行評審

10 引文 斯高帕斯(Scopus)

摘要

Covalently cross-linked pilus polymers displayed on the cell surface of Gram-positive bacteria are assembled by class C sortase enzymes. These pilus-specific transpeptidases located on the bacterial membrane catalyze a two-step protein ligation reaction, first cleaving the LPXTG motif of one pilin protomer to form an acylenzyme intermediate and then joining the terminal Thr to the nucleophilic Lys residue residing within the pilin motif of another pilin protomer. To date, the determinants of class C enzymes that uniquely enable them to construct pili remain unknown. Here, informed by high-resolution crystal structures of corynebacterial pilus-specific sortase (SrtA) and utilizing a structural variant of the enzyme (SrtA2M), whose catalytic pocket has been unmasked by activating mutations, we successfully reconstituted in vitro polymerization of the cognate major pilin (SpaA). Mass spectrometry, electron microscopy, and biochemical experiments authenticated that SrtA2M synthesizes pilus fibers with correct Lys-Thr isopeptide bonds linking individual pilins via a thioacyl intermediate. Structural modeling of the SpaA-SrtA-SpaA polymerization intermediate depicts SrtA2M sandwiched between the N- and C-terminal domains of SpaA harboring the reactive pilin and LPXTG motifs, respectively. Remarkably, the model uncovered a conserved TP(Y/L)XIN(S/T)H signature sequence following the catalytic Cys, in which the alanine substitutions abrogated crosslinking activity but not cleavage of LPXTG. These insights and our evidence that SrtA2M can terminate pilus polymerization by joining the terminal pilin SpaB to SpaA and catalyze ligation of isolated SpaA domains in vitro provide a facile and versatile platform for protein engineering and bio-conjugation that has major implications for biotechnology.

原文English
頁(從 - 到)E5477-E5486
期刊Proceedings of the National Academy of Sciences of the United States of America
115
發行號24
DOIs
出版狀態Published - 2018 六月 12

All Science Journal Classification (ASJC) codes

  • 多學科

指紋

深入研究「In vitro reconstitution of sortase-catalyzed pilus polymerization reveals structural elements involved in pilin cross-linking」主題。共同形成了獨特的指紋。

引用此