Journal of Biochemistry Advance Access published online on October 27, 2007
Journal of Biochemistry, doi:10.1093/jb/mvm195
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
© 2007 The Japanese Biochemical Society
Characterization of the
-Helix Region in Domain 3 of the Hemolytic Lectin CEL-III: Implications for Self-Oligomerization and Hemolytic Processes
Department of Applied Chemistry, Faculty of Engineering, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521
*To whom correspondence should be addressed: prof. Tomomitsu Hatakeyama, Fax: +81-95-819-2684, E-mail: thata{at}nagasaki-u.ac.jp
Received June 2, 2007; Accepted October 7, 2007
| Abstract |
|---|
Summary:
CEL-III is a hemolytic lectin, which has two ß-trefoil domains (domains 1 and 2) and a ß-sheet-rich domain (domain 3). In domain 3 (residues 284-432), there is a hydrophobic region containing two
–helices (H8 and H9, residues 317-357) and a loop between them, in which alternate hydrophobic residues, especially Val residues, are present. To elucidate the role of the
–helix region in the hemolytic process, peptides corresponding to different parts of this region were synthesized and characterized. The peptides containing the sequence that corresponded to the loop and second
–helix (H9) showed the strongest antibacterial activity for Staphylococcus aureus and Bacillus subtilis through a marked permeabilization of the bacterial cell membrane. The recombinant glutathione S-transferase (GST)-fusion proteins containing domain 3 or the
–helix region peptide formed self-oligomers, whereas mutations in the alternate Val residues in the
–helix region lead to decreased oligomerization ability of the fusion proteins. These results suggest that the
-helix region, particularly its alternate Val residues are important for oligomerization of CEL-III in target cell membranes, which is also required for a subsequent hemolytic action.
Key Words: antibacterial peptide, Ca2+-dependent lectin, hemolysin, oligomerization, small-angle X-ray scattering