Molecular Insight into Mechanism of Antimicrobial Action of the b-Hairpin Peptide Arenicin: Specific Oligomerization in Detergent Micelles Tatiana V. Ovchinnikova, 1 Zakhar O. Shenkarev, 1 Sergey V. Balandin, 1 Kirill D. Nadezhdin, 1 Alexander S. Paramonov, 1 Vladimir N. Kokryakov, 2 Alexander S. Arseniev 1 1 Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya str. 16/10, 117997 Moscow, Russia 2 Institute of Experimental Medicine, Russian Academy of Medical Sciences, Academica Pavlova str. 12, 197376 Saint-Petersburg, Russia Received 31 July 2007; revised 22 September 2007; accepted 5 October 2007 Published online 15 October 2007 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/bip.20865 This article was originally published online as an accepted preprint. The ‘‘Published Online’’ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com Molecular Insight into Mechanism of Antimicrobial Action of the b-Hairpin Peptide Arenicin: Specific Oligomerization in Detergent Micelles This article is dedicated to the memory of Elkan Blout, a world class scientist, an uncommon man, and a great friend of our family. Follow- ing the first meeting in 1970 at a Gordon conference on peptides, Elkan Blout and Yuri Ovchinnikov, Vice President of the USSR Acad- emy of Sciences, became increasingly friendly and soon very close friends who visited each other many times in laboratories and homes. In 1976 Elkan Blout was elected a Foreign Member of the USSR Acad- emy of Sciences. The major research interests of Elkan Blout included peptides structural analysis. The present work focuses on study of the marine invertebrate peptide arenicin. The syntagm ‘‘marine’’ and ‘‘peptide’’ brings nice memories about Elkan as a proficient captain of his sailboat ‘‘Peptide’’. I also remember Elkan during the FEBS meet- ing in Moscow in 1984, when he planted trees near a new building of our Institute among a bevy of world-renowned scientists, such as Linus Pauling and Dorothy Hodgkin. Elkan Blout was a remarkable man with many outstanding qualities, and he will long be remem- bered by scientists from around the world. Correspondence to: Tatiana V. Ovchinnikova; e-mail: ovch@ibch.ru ABSTRACT: Arenicins are 21-residue cationic antimicrobial peptides isolated from marine polychaeta Arenicola marina. The peptides exhibit potent broad-spectrum antimicrobial activity. In water solution arenicin-2 adopts a b-hairpin conformation, stabilized by one disulfide and nine hydrogen bonds. To determine the propensity for the peptide oligomerization in membrane mimetic systems, the recombinant arenicin-2 was overexpressed as a fused form in Escherichia coli. The arenicin-2 oligomerization and intermolecular packing in membrane mimicking environment were investigated using high-resolution NMR spectroscopy. The present studies show that arenicin-2 preserves a b-hairpin structure and forms asymmetric dimers upon incorporation into the dodecylphosphocholine micelle. Two monomers of arenicin-2 are aligned parallel to each other by the N-terminal strands of the b-hairpin (CN::NC type of association). Polyacrylamide gel electrophoresis analysis indicated that in environment of anionic SDS micelles the arenicin-2 might undergo further oligomerization and form tetramers. Our results afford further molecular insight into possible mechanism of antimicrobial action of arenicins. # 2007 Wiley Periodicals, Inc. Biopolymers 89: 455–464, 2008. Keywords: antimicrobial peptide; arenicin; lugworm; Arenicola marina; marine invertebrate; expression; recombinant; fusion protein; purification; folding; oligomerization; NMR; b-hairpin Contract grant sponsors: Russian Foundation for Basic Research (06-04- 49409, 06-04-08267), Russian Federal Agency for Science and Innovations (02.522.11.2007) V V C 2007 Wiley Periodicals, Inc. Biopolymers Volume 89 / Number 5 455