4E83

Crystal structure of human alpha-defensin 5, HD5 (Leu29NLe mutant)

Summary for 4E83

• Entry DOI: 10.2210/pdb4e83/pdb
• Related: 1ZMP 4E82 4E86
• Descriptor: Defensin-5, CHLORIDE ION (3 entities in total)
• Functional Keywords: beta-sheet structure, antimicrobial peptide, leu29nle mutant, paneth cells, antimicrobial protein
• Biological source: Homo sapiens (human)
• Cellular location: Secreted: Q01523
• Total number of polymer chains: 2
• Total formula weight: 7223.91

Authors

Pazgier, M. (deposition date: 2012-03-19, release date: 2012-05-16, Last modification date: 2024-11-20)

Primary citation

Rajabi, M.,Ericksen, B.,Wu, X.,de Leeuw, E.,Zhao, L.,Pazgier, M.,Lu, W.
Functional determinants of human enteric {alpha}-defensin HD5: crucial role for hydrophobicity at dimer interface.
J.Biol.Chem., 287:21615-21627, 2012

PubMed Abstract: Human α-defensins are cationic peptides that self-associate into dimers and higher-order oligomers. They bind protein toxins, such as anthrax lethal factor (LF), and kill bacteria, including Escherichia coli and Staphylococcus aureus, among other functions. There are six members of the human α-defensin family: four human neutrophil peptides, including HNP1, and two enteric human defensins, including HD5. We subjected HD5 to comprehensive alanine scanning mutagenesis. We then assayed LF binding by surface plasmon resonance, LF activity by enzyme kinetic inhibition, and antibacterial activity by the virtual colony count assay. Most mutations could be tolerated, resulting in activity comparable with that of wild type HD5. However, the L29A mutation decimated LF binding and bactericidal activity against Escherichia coli and Staphylococcus aureus. A series of unnatural aliphatic and aromatic substitutions at position 29, including aminobutyric acid (Abu) and norleucine (Nle) correlated hydrophobicity with HD5 function. The crystal structure of L29Abu-HD5 depicted decreased hydrophobic contacts at the dimer interface, whereas the Nle-29-HD5 crystal structure depicted a novel mode of dimerization with parallel β strands. The effect of mutating Leu(29) is similar to that of a C-terminal hydrophobic residue of HNP1, Trp(26). In addition, in order to further clarify the role of dimerization in HD5 function, an obligate monomer was generated by N-methylation of the Glu(21) residue, decreasing LF binding and antibacterial activity against S. aureus. These results further characterize the dimer interface of the α-defensins, revealing a crucial role of hydrophobicity-mediated dimerization.

PubMed: 22573326
DOI: 10.1074/jbc.M112.367995

Experimental method

X-RAY DIFFRACTION (1.9 Å)