Host-defence skin peptides of the Australian Streambank Froglet Crinia riparia: isolation and sequence determination by positive and negative ion electrospray mass spectrometry.
A combination of positive and negative ion electrospray mass spectrometry (ES-MS) together with automated Edman sequencing has been used to determine the amino acid sequences of the host-defence peptides from the skin glands of the froglet Crinia riparia. The peptides are called riparins. Of the eight peptides isolated, five are neuropeptides containing intramolecular disulfide linkages; e.g. the major peptide riparin 1.4 (FFLPPCAYKGTC-OH). Positive ion ES-MS identifies the five residues of riparin 1.4 outside the disulfide moiety, but provides no information on the sequence within the disulfide ring. In contrast, the negative ion dissociations of the [M-H]- ion of riparin 1.4 identify the --S-S-- link by loss of H2S2 from the [M-H]- ion, and also provide the sequence within the disulfide unit. Other peptides are riparin 2.1 [(IIEKLVNTALGLLSGL-NH2), a narrow-spectrum antibiotic], signiferin 3.1 [(GIAEFLNYIKSKA-NH2), an nNOS inhibitor] and riparin 5.1 [IVSYPDDAGEHAHKMG-NH2], which shows no neuropeptide, antibiotic or nNOS activity.
Maselli
Vita M
VM
Department of Chemistry, The University of Adelaide, South Australia, 5005.
Bilusich
Daniel
D
Bowie
John H
JH
Tyler
Michael J
MJ
D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000032:analysis*; D011898:Ranidae / Q000378:metabolism*; D020539:Sequence Analysis, Protein; D012867:Skin / Q000737:chemistry / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D009479:Neuropeptides