Title: Polyglycine hydrolases secreted by pathogenic fungi Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2014
Publication Date: July 30, 2014
Citation: Naumann, T.A., Wicklow, D.T., Ward, T.J., Naldrett, M.J., Price, N.P. 2014. Polyglycine hydrolases secreted by pathogenic fungi [abstract]. Symposium of The Protein Society. Technical Abstract: Pathogens are known to produce proteases that target host defense proteins. Here we describe polyglycine hydrolases, fungal proteases that selectively cleave glycine-glycine peptide bonds within the polyglycine interdomain linker of targeted plant defense chitinases. Polyglycine hydrolases were purified from two fungal pathogens, Bipolaris zeicola (Bz-cmp) and Epicoccum sorghi (Es-cmp). Both proteases were shown to cleave three different corn (Zea mays) chitinase substrates. These substrates have interdomain polyglycine linkers with as many as 14 consecutive glycines. MALDI-TOF MS analysis of peptide products indicated that polyglycine hydrolases cleave multiple peptide bonds within the polyglycine linker regions. The peptides produced and their abundance varied with both protease and substrate. Removal of the amino-terminal 29 amino acids from substrate chitinases resulted in loss of activity. This suggests that polyglycine hydrolases recognize the short, amino-terminal domain of targeted chitinases through exosite interactions. To identify these novel proteases, a draft genome sequence was generated from E. sorghi genomic DNA and purified Es-cmp was subjected to peptide mass fingerprinting. Two candidate proteases were identified. We are cloning the cDNAs and creating heterologous expression strains to produce recombinant proteins. Recombinant proteins will be tested for the ability to cleave chitinase polyglycine linkers. Our description of polyglycine hydrolase activity improves understanding of how proteases can evolve to target specific proteins.