HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplemental Data Buy All Versions of this Article: fj.08-122317v1 fj.08-122317v2 23/4/1230    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gao, B. Articles by Zhu, S. Search for Related Content PubMed PubMed Citation Articles by Gao, B. Articles by Zhu, S.

Structural and functional characterization of two genetically related meucin peptides highlights evolutionary divergence and convergence in antimicrobial peptides

Bin Gao^*, Patrick Sherman, Lan Luo^*, John Bowie and Shunyi Zhu^*,1

^* Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China; and

Department of Chemistry, The University of Adelaide, Adelaide, South Australia, Australia

¹Correspondence: Institute of Zoology, Chinese Academy of Sciences, Datun Rd., Chaoyang District, Beijing 100101, China. E-mail: zhusy{at}ioz.ac.cn

Both vertebrates and invertebrates employ -helical antimicrobial peptides (AMPs) as an essential component of their innate immune system. However, evolutionary relation of these immune molecules remains unresolved. Venoms, as key weapons of venomous arthropods for prey and defense, receive increasing recognition as an emerging source of such peptides. From a cDNA library prepared from the venom gland of the scorpion Mesobuthus eupeus, clones encoding precursors of two new AMPs, named meucin-13 (IFGAIAGLLKNIF-NH₂) and meucin-18 (FFGHLFKLATKIIPSLFQ), have been isolated. The precursor of meucins consists of a signal peptide, a mature peptide, and an acidic propeptide, in which dibasic residues as the typical processing signal are located between the mature and propeptide. Meucin-13 is an ortholog of several previously described AMPs from scorpion venom and has also detectable sequence similarity to temporins, a large family of AMPs from frog skin, whereas meucin-18 displays some similarity to AMPs from diverse origin including arthropod venoms, fish mast cells, and frog skins. These two meucin peptides form -helical structure in the presence of 50% trifluoroethanol (TFE), a membrane-mimicking environment, as identified by circular dichroism (CD) spectroscopy. This finding is further verified by their NMR structures that show a typical -helical amphipathic design, a structural prerequisite for cytolytic activity. Meucins exhibit extensive cytolytic effects on both prokaryotic and eukaryotic cells (gram⁺ and gram^– bacteria, fungi, yeasts, rabbit erythrocytes, and rat dorsal root ganglion cells) at micromolar concentrations. It is remarkable that muecin-18 was 2- to >14-fold more potent than meucin-13 against nearly all the cells tested. Structural differences in hydrophilic/hydrophobic balance and cationic amino acid location between two meucins could account for their differential potency. Despite these differences, commonalities at precursor organization, three-dimensional structure, and biological function suggests that meucins are two evolutionarily related AMPs and likely originated from a common ancestor by gene duplication. Our work presented here also provides new insights into an evolutionary link among AMPs from invertebrates and vertebrates and clues for evolutionary convergence between AMPs and virus fusion domains.—Gao, B., Sherman, P., Luo, L., Bowie, J., Zhu, S. Structural and functional characterization of two genetically related meucin peptides highlights evolutionary divergence and convergence in antimicrobial peptides.

Key Words: innate immunity • NMR structure • venomous arthropod • gene cloning • virus fusion domain