The α-defensin salt-bridge induces backbone stability to facilitate folding and confer proteolytic resistance

Andersson, Hakan S., Figueredo, Sharel M., Haugaard-Kedstrom, Linda M., Bengtsson, Elina, Daly, Norelle L., Qu, Xiaoqing, Craik, David J., Ouellette, Andre J. and Rosengren, K. Johan (2012) The α-defensin salt-bridge induces backbone stability to facilitate folding and confer proteolytic resistance. Amino Acids, 43 4: 1471-1483. doi:10.1007/s00726-012-1220-3

Author Andersson, Hakan S.
Figueredo, Sharel M.
Haugaard-Kedstrom, Linda M.
Bengtsson, Elina
Daly, Norelle L.
Qu, Xiaoqing
Craik, David J.
Ouellette, Andre J.
Rosengren, K. Johan
Title The α-defensin salt-bridge induces backbone stability to facilitate folding and confer proteolytic resistance
Journal name Amino Acids   Check publisher's open access policy
ISSN 1438-2199
Publication date 2012
Sub-type Article (original research)
DOI 10.1007/s00726-012-1220-3
Volume 43
Issue 4
Start page 1471
End page 1483
Total pages 13
Place of publication Vienna, Austria
Publisher Springer
Collection year 2013
Language eng
Formatted abstract
Salt-bridge interactions between acidic and basic amino acids contribute to the structural stability of proteins and to protein–protein interactions. A conserved salt-bridge is a canonical feature of the α-defensin antimicrobial peptide family, but the role of this common structural element has not been fully elucidated. We have investigated mouse Paneth cell α-defensin cryptdin-4 (Crp4) and peptide variants with mutations at Arg7 or Glu15 residue positions to disrupt the salt-bridge and assess the consequences on Crp4 structure, function, and stability. NMR analyses showed that both (R7G)-Crp4 and (E15G)-Crp4 adopt native-like structures, evidence of fold plasticity that allows peptides to reshuffle side chains and stabilize the structure in the absence of the salt-bridge. In contrast, introduction of a large hydrophobic side chain at position 15, as in (E15L)-Crp4 cannot be accommodated in the context of the Crp4 primary structure. Regardless of which side of the salt-bridge was mutated, salt-bridge variants retained bactericidal peptide activity with differential microbicidal effects against certain bacterial cell targets, confirming that the salt-bridge does not determine bactericidal activity per se. The increased structural flexibility induced by salt-bridge disruption enhanced peptide sensitivity to proteolysis. Although sensitivity to proteolysis by MMP7 was unaffected by most Arg7 and Glu15 substitutions, every salt-bridge variant was degraded extensively by trypsin. Moreover, the salt-bridge facilitates adoption of the characteristic α-defensin fold as shown by the impaired in vitro refolding of (E15D)-proCrp4, the most conservative salt-bridge disrupting replacement. In Crp4, therefore, the canonical α-defensin salt-bridge facilitates adoption of the characteristic α-defensin fold, which decreases structural flexibility and confers resistance to degradation by proteinases.
Keyword Defensin
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published online: 29 January 2012

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2013 Collection
School of Biomedical Sciences Publications
Institute for Molecular Bioscience - Publications
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Citation counts: TR Web of Science Citation Count  Cited 11 times in Thomson Reuters Web of Science Article | Citations
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Created: Wed, 01 Aug 2012, 15:28:45 EST by Susan Allen on behalf of Institute for Molecular Bioscience