Three-dimensional structure of RK-1: a novel alpha-defensin peptide.
NMR spectroscopy and simulated annealing calculations have been used to determine the three-dimensional structure of RK-1, an antimicrobial peptide from rabbit kidney recently discovered from homology screening based on the distinctive physicochemical properties of the corticostatins/defensins. RK-1 consists of 32 residues, including six cysteines arranged into three disulfide bonds. It exhibits antimicrobial activity against Escherichia coli and activates Ca(2+) channels in vitro. Through its physicochemical similarity, identical cysteine spacing, and linkage to the corticostatins/defensins, it was presumed to be a member of this family. However, RK-1 lacks both a large number of arginines in the primary sequence and a high overall positive charge, which are characteristic of this family of peptides. The three-dimensional solution structure, determined by NMR, consists of a triple-stranded antiparallel beta-sheet and a series of turns and is similar to the known structures of other alpha-defensins. This has enabled the definitive classification of RK-1 as a member of this family of antimicrobial peptides. Ultracentrifuge measurements confirmed that like rabbit neutrophil defensins, RK-1 is monomeric in solution, in contrast to human neutrophil defensins, which are dimeric.
McManus
A M
AM
Centre for Drug Design and Development, Institute for Molecular Bioscience and Department of Biochemistry, University of Queensland, Brisbane, Queensland 4072, Australia.
Dawson
N F
NF
Wade
J D
JD
Carrington
L E
LE
Winzor
D J
DJ
Craik
D J
DJ
D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry; D018360:Crystallography, X-Ray; D019281:Dimerization; D006801:Humans; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011817:Rabbits; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D023084:alpha-Defensins / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification
D000890:Anti-Infective Agents; C405106:RK-1 peptide; D023084:alpha-Defensins