Peptide defenses of the Cascades frog Rana cascadae: implications for the evolutionary history of frogs of the Amerana species group.
The Cascades frog Rana cascadae belongs to the Amerana (or Rana boylii) group that includes six additional species from western North America (R. aurora, R. boylii, R. draytonii, R. luteiventris, R. muscosa, and R. pretiosa). R. cascadae is particularly susceptible to pathogenic microorganisms in the environment and populations have declined precipitously in parts of its range so that the protection afforded by dermal antimicrobial peptides may be crucial to survival of the species. Peptidomic analysis of norepinephrine-stimulated skin secretions led to the identification of six peptides with differential cytolytic activities that were present in high abundance. Structural characterization showed that they belonged to the ranatuerin-2 (one peptide), brevinin-1 (one peptide), and temporin (four peptides) families. Ranatuerin-2CSa (GILSSFKGVAKGVAKDLAGKLLETLKCKITGC) and brevinin-1CSa (FLPILAGLAAKIVPKLFCLATKKC) showed broad spectrum antibacterial activity (MIC</=32microM against Escherichia coli and Staphylococcus aureus) but only brevinin-1CSa was strongly hemolytic against human erythrocytes (LC(50)=5microM). The taxonomy of ranid frogs is currently in a considerable state of flux. The ranatuerin-2 gene is expressed in all members of the Amerana group studied to-date and cladistic analysis based upon a comparison of the amino acid sequences of this peptide indicates that R. cascadae, R. muscosa and R. aurora form a clade that is distinct from one containing R. draytonii, R. boylii, and R. luteiventris. This conclusion is consistent with previous analyses based upon comparisons of the nucleotide sequences of mitochondrial genes.
Conlon
J Michael
JM
Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al-Ain, United Arab Emirates. jmconlon@uaeu.ac.ae
Al-Dhaheri
Ahmed
A
Al-Mutawa
Eissa
E
Al-Kharrge
Rokaya
R
Ahmed
Eman
E
Kolodziejek
Jolanta
J
Nowotny
Norbert
N
Nielsen
Per F
PF
Davidson
Carlos
C
D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D017124:Conserved Sequence; D004220:Disulfides / Q000737:chemistry; D004912:Erythrocytes / Q000187:drug effects; D019143:Evolution, Molecular; D006801:Humans; D007928:Lethal Dose 50; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D011898:Ranidae / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D004220:Disulfides