D-amino acid residue in a defensin-like peptide from platypus venom: effect on structure and chromatographic properties.
The recent discovery that the natriuretic peptide OvCNPb (Ornithorhynchus venom C-type natriuretic peptide B) from platypus (Ornithorynchus anatinus) venom contains a D-amino acid residue suggested that other D-amino-acid-containing peptides might be present in the venom. In the present study, we show that DLP-2 (defensin-like peptide-2), a 42-amino-acid residue polypeptide in the platypus venom, also contains a D-amino acid residue, D-methionine, at position 2, while DLP-4, which has an identical amino acid sequence, has all amino acids in the L-form. These findings were supported further by the detection of isomerase activity in the platypus gland venom extract that converts DLP-4 into DLP-2. In the light of this new information, the tertiary structure of DLP-2 was recalculated using a new structural template with D-Met2. The structure of DLP-4 was also determined in order to evaluate the effect of a D-amino acid at position 2 on the structure and possibly to explain the large retention time difference observed for the two molecules in reverse-phase HPLC. The solution structures of the DLP-2 and DLP-4 are very similar to each other and to the earlier reported structure of DLP-2, which assumed that all amino acids were in the L-form. Our results suggest that the incorporation of the D-amino acid at position 2 has minimal effect on the overall fold in solution.
Torres
Allan M
AM
School of Molecular and Microbial Biosciences, University of Sydney, NSW 2006, Australia.
Tsampazi
Chryssanthi
C
Geraghty
Dominic P
DP
Bansal
Paramjit S
PS
Alewood
Paul F
PF
Kuchel
Philip W
PW
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis* / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D023082:Defensins / Q000737:chemistry* / Q000378:metabolism*; D007535:Isomerases / Q000378:metabolism; D007536:Isomerism; D008297:Male; D008969:Molecular Sequence Data; D010987:Platypus; D011487:Protein Conformation; D014688:Venoms / Q000737:chemistry*
D000596:Amino Acids; D023082:Defensins; D014688:Venoms; D007535:Isomerases