title: Amino acid sequence of piratoxin-I, a myotoxin from Bothrops pirajai snake venom, and its biological activity after alkylation with p-bromophenacyl bromide.
abstract: The complete sequence of the 121 amino acid residues of piratoxin-I (PrTX-I), a phospholipase A2 (PLA2)-like myotoxin from Bothrops pirajai snake (Bahia jararacussu) venom, is reported. From the sequence, an M, of 13,825 and an approximate pI of 8.3 were calculated. PrTX-I shows a high sequence homology with Lys-49 myotoxins from other bothropic (approximately 95%) and nonbothropic (approximately 80%) venoms, but only 70-75% homology when aligned with the catalytically active Asp-49 PLA2s. When compared with bothropstoxin-I from Bothropsjararacussu, which is morphologically almost identical to B. pirajai, only two changes out of 121 total amino acid residues have been observed. The approximate minimal lethal dose LD50 (mice, i.p., 24 hr) of PrTX-I was 8 (6.8-9.1) mg/kg, and the minimal edematogenic dose (MED) in a rat paw model was 39.5+/-1.8 ug. After alkylation of His-48 with p-bromophenacyl bromide, the MED was 40.1+/-1.9 ug, but up to 4 LD50 were unable to cause death in any of a group of eight mice after 72 hr. Therefore the edematogenic activity was retained and apparently did not involve His-48, suggesting that at least two biologically active sites are present in PrTX-I.
authors.affiliation: Department of Biochemistry, Institute of Biology, UNICAMP, Campinas-SP, Brazil.
authors.forename: M H
authors.initials: MH
authors.lastname: Toyama
authors.forename: A M
authors.initials: AM
authors.lastname: Soares
authors.forename: C A
authors.initials: CA
authors.lastname: Vieira
authors.forename: J C
authors.initials: JC
authors.lastname: Novello
authors.forename: B
authors.initials: B
authors.lastname: Oliveira
authors.forename: J R
authors.initials: JR
authors.lastname: Giglio
authors.forename: S
authors.initials: S
authors.lastname: Marangoni
mesh_terms: D000098:Acetophenones / Q000494:pharmacology*; D000478:Alkylation; D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003435:Crotalid Venoms / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D054501:Group II Phospholipases A2; D006639:Histidine; D007928:Lethal Dose 50; D051379:Mice; D008969:Molecular Sequence Data; D010741:Phospholipases A / Q000737:chemistry*; D054467:Phospholipases A2; D051381:Rats; D030162:Reptilian Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D000098:Acetophenones; D003435:Crotalid Venoms; D004791:Enzyme Inhibitors; D030162:Reptilian Proteins; C078097:bothropstoxin; D006639:Histidine; C114085:piratoxin I; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2; C006821:4-bromophenacyl bromide