Role of cysteine residues and disulfide bonds in the activity of a legume root nodule-specific, cysteine-rich peptide

Andreas F Haag, Bernhard Kerscher, Sergio Dall'Angelo, Monica Sani, Renato Longhi, Mikhail Baloban, Heather M Wilson, Peter Mergaert, Matteo Zanda, Gail P Ferguson

Research output: Contribution to journalArticlepeer-review

62 Citations (Scopus)


The root nodules of certain legumes including Medicago truncatula produce >300 different nodule-specific cysteine-rich (NCR) peptides. Medicago NCR antimicrobial peptides (AMPs) mediate the differentiation of the bacterium, Sinorhizobium meliloti into a nitrogen-fixing bacteroid within the legume root nodules. In vitro, NCR AMPs such as NCR247 induced bacteroid features and exhibited antimicrobial activity against S. meliloti. The bacterial BacA protein is critical to prevent S. meliloti from being hypersensitive toward NCR AMPs. NCR AMPs are cationic and have conserved cysteine residues, which form disulfide (S–S) bridges. However, the natural configuration of NCR AMP S–S bridges and the role of these in the activity of the peptide are unknown. In this study, we found that either cysteine replacements or S–S bond modifications influenced the activity of NCR247 against S. meliloti. Specifically, either substitution of cysteines for serines, changing the S–S bridges from cysteines 1–2, 3–4 to 1–3, 2–4 or oxidation of NCR247 lowered its activity against S. meliloti. We also determined that BacA specifically protected S. meliloti against oxidized NCR247. Due to the large number of different NCRs synthesized by legume root nodules and the importance of bacterial BacA proteins for prolonged host infections, these findings have important implications for analyzing the function of these novel peptides and the protective role of BacA in the bacterial response toward these peptides.
Original languageEnglish
Pages (from-to)10791-10798
Number of pages8
JournalThe Journal of Biological Chemistry
Issue number14
Early online date17 Feb 2012
Publication statusPublished - 30 Mar 2012


  • antimicrobial peptides
  • bacteria
  • microbiology
  • peptide conformation
  • symbiosis
  • BacA
  • defensins
  • nodule-specific, cysteine-rich peptides
  • rhizobia
  • Sinorhizobium meliloti


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