ORIGINAL ARTICLE LyeTx I, a potent antimicrobial peptide from the venom of the spider Lycosa erythrognatha D. M. Santos • R. M. Verly • D. Pilo ´-Veloso • M. de Maria • M. A. R. de Carvalho • P. S. Cisalpino • B. M. Soares • C. G. Diniz • L. M. Farias • D. F. F. Moreira • F. Fre ´zard • M. P. Bemquerer • A. M. C. Pimenta • M. E. de Lima Received: 19 September 2009 / Accepted: 29 October 2009 / Published online: 28 November 2009 Ó Springer-Verlag 2009 Abstract LyeTx I, an antimicrobial peptide isolated from the venom of Lycosa erythrognatha, known as wolf spider, has been synthesised and its structural profile studied by using the CD and NMR techniques. LyeTx I has shown to be active against bacteria (Escherichia coli and Staphylo- coccus aureus) and fungi (Candida krusei and Crypto- coccus neoformans) and able to alter the permeabilisation of L-a-phosphatidylcholine-liposomes (POPC) in a dose- dependent manner. In POPC containing cholesterol or ergosterol, permeabilisation has either decreased about five times or remained unchanged, respectively. These results, along with the observed low haemolytic activity, indicated that antimicrobial membranes, rather than vertebrate membranes seem to be the preferential targets. However, the complexity of biological membranes compared to lip- osomes must be taken in account. Besides, other membrane components, such as proteins and even specific lipids, cannot be discarded to be important to the preferential action of the LyeTx I to the tested microorganisms. The secondary structure of LyeTx I shows a small random-coil region at the N-terminus followed by an a-helix that reached the amidated C-terminus, which might favour the peptide-membrane interaction. The high activity against bacteria together with the moderate activity against fungi A.M.C. Pimenta and M.E. de Lima have contributed equally to this work Electronic supplementary material The online version of this article (doi:10.1007/s00726-009-0385-x) contains supplementary material, which is available to authorized users. D. M. Santos Á D. F. F. Moreira Á A. M. C. Pimenta Á M. E. de Lima (&) Lab. Venenos e Toxinas Animais, Departamento de Bioquı ´mica e Imunologia, Instituto de Cie ˆncias Biolo ´gicas, Universidade Federal de Minas Gerais, Av. Anto ˆnio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil e-mail: melenalima@icb.ufmg.br; lima.mariaelena@gmail.com R. M. Verly Á D. Pilo ´-Veloso Departamento de Quı ´mica, ICEX, Universidade Federal de Minas Gerais, Av. Anto ˆnio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil M. de Maria Departamento de Zoologia, Instituto de Cie ˆncias Biolo ´gicas, Universidade Federal de Minas Gerais, Av. Anto ˆnio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil M. A. R. de Carvalho Á P. S. Cisalpino Á B. M. Soares Á L. M. Farias Departamento de Microbiologia, Instituto de Cie ˆncias Biolo ´gicas, Universidade Federal de Minas Gerais, Av. Anto ˆnio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil C. G. Diniz Departamento de Parasitologia, Microbiologia e Imunologia, ICB, Universidade Federal de Juiz de Fora, 36036-900 Juiz de Fora, Minas Gerais, Brazil F. Fre ´zard Departamento de Fisiologia e Biofı ´sica, Instituto de Cie ˆncias Biolo ´gicas, Universidade Federal de Minas Gerais, Av. Anto ˆnio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil M. P. Bemquerer Embrapa Recursos Gene ´ticos e Biotecnologia, PqEB, Av. W5 Norte (final), 70770-900 Brası ´lia, Distrito Federal, Brazil 123 Amino Acids (2010) 39:135–144 DOI 10.1007/s00726-009-0385-x