Polyglycine hydrolases: Fungal β-lactamase-like endoproteases that cleave polyglycine regions within plant class IV chitinases

Todd A. Naumann, Michael J. Naldrett, Todd J. Ward, Neil P.J. Price

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

Polyglycine hydrolases are secreted fungal proteases that cleave glycine-glycine peptide bonds in the inter-domain linker region of specific plant defense chitinases. Previously, we reported the catalytic activity of polyglycine hydrolases from the phytopathogens Epicoccum sorghi (Es-cmp) and Cochliobolus carbonum (Bz-cmp). Here we report the identity of their encoding genes and the primary amino acid sequences of the proteins responsible for these activities. Peptides from a tryptic digest of Es-cmp were analyzed by LC-MS/MS and the spectra obtained were matched to a draft genome sequence of E. sorghi. From this analysis, a 642 amino acid protein containing a predicted β-lactamase catalytic region of 280 amino acids was identified. Heterologous strains of the yeast Pichia pastoris were created to express this protein and its homolog from C. carbonum from their cDNAs. Both strains produced recombinant proteins with polyglycine hydrolase activity as shown by SDS-PAGE and MALDI-MS based assays. Site directed mutagenesis was used to mutate the predicted catalytic serine of Es-cmp to glycine, resulting in loss of catalytic activity. BLAST searching of publicly available fungal genomes identified full-length homologous proteins in 11 other fungi of the class Dothideomycetes, and in three fungi of the related class Sordariomycetes while significant BLAST hits extended into the phylum Basidiomycota. Multiple sequence alignment led to the identification of a network of seven conserved tryptophans that surround the β-lactamase-like region. This is the first report of a predicted β-lactamase that is an endoprotease.

Original languageEnglish (US)
Pages (from-to)1147-1157
Number of pages11
JournalProtein Science
Volume24
Issue number7
DOIs
StatePublished - Jul 1 2015

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Keywords

  • PAMP-triggered immunity
  • SXXK motif
  • effector-triggered defense
  • effectors
  • family S12
  • host-pathogen interactions
  • penicillin-binding protein
  • plant defense
  • protease
  • proteinase
  • β-lactamase

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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