Cupiennins are a group of smallcytolytic peptides from the venom of thewandering spiderCupiennius salei. They are known to have highbactericidal,insecticidal andhaemolytic activities. They are chemically cationicα-helical peptides.[1] They were isolated and identified in 2002 as a family of peptides called cupiennin 1. The sequence was determined by a process calledEdman degradation, and the family consists of cupiennin 1a, cupiennin 1b, cupiennin 1c, and cupiennin 1d. The amino acid sequences of cupiennin 1b, c, and d were obtained by a combination of sequence analysis andmass spectrometric measurements of comparative tryptic peptide mapping. Even though they are not strong toxins, they do enhance the effect of the spider venom bysynergistically enhancing other components of the venom, suchCSTX.[2]
All cupiennins are composed of 35 amino acid residues and are characterised by a more hydrophobic N-terminal chain region and a C-terminus composed preferentially of polar and charged residues. Their distinguishing feature is the absence ofcysteine. On the basis of the absence or presence ofproline, cupiennins are divided into two families cupiennin 1 family and cupiennin 2 family.[3]
Cupiennin 1 family is the more well-known group, and consists of at least four peptides, such as cupiennin 1a, 1b, 1c, and 1d. Cupiennin 1a (M-ctenitoxin-Cs1a) is the most abundant and has a molecular mass of 3798.63 Da. Cupiennin 1b is less abundant and has a size of 3800.25 Da. Cupiennin 1c (3769.75 Da) and 1d (3795.13) are in extremely low concentrations. These peptides are highly cationic, made up of similar amino acids, but different in the N- and C-terminal ends. The hydrophobic N-terminal is characterised by six repeats of four amino acids, which are in a conserved sequence: position 1 is alwayslysine; position 2 is variable; position 3 is always a hydrophobic amino acid orglycine, and in position 4 is eitheralanine orvaline.[2] All members have high antibacterial activity againstGram-positive as well asGram-negative bacteria at a range of 0.16 to 5 mM concentration. They also exhibit a cytolytic activity between 14.5–24.4 mM on humanerythrocytes. They also haveantiprotozoal activity againstTrypanosoma cruzi andmalarial parasite. They are insecticidal, but not as strong as the CSTX-1, another peptide of the same venom.[4] These properties are modulated by theN-terminus.[5]
Cupiennin 2 family is less well understood, but it also comprises at least four peptides. In fact, members of this family were discovered earlier in 1994 as member of the CSTX peptides. Upon the discovery of cupiennin 1 family, CSTX-3, -4, -5, and -6 are reclassified as cupiennins. This is because of their basic chemical similarities, such as the amino acid residues. They are characterised by the presence of at least one proline. Cupiennin 2a is the best studied. It has a molecular mass of 3701.05 Da, and shows weak cytolytic, bactericidal and insecticidal activities.[3]