Investigation of toroidal pore and oligomerization by melittin using transmission electron microscopy.
We studied the effects of melittin on various cell wall components and vesicles of various lipid compositions. To interact with the cytoplasmic membrane, melittin must traverse the cell wall, which is composed of oligosaccharides. Here, we found that melittin had a strong affinity for chitin, peptidoglycan, and lipopolysaccharide. We further examined the influence of lipid compositions on the lysis of the membranes by melittin. The result showed that melittin bound better to negatively charged than to zwitterionic lipid vesicles but was more potent at inducing leakage from zwitterionic lipid vesicles. Our studies further indicated that the oligomeric state of melittin varied between tetramers and octamers during the formation of toroidal pores. Dextran leakage experiments confirmed the formation and dimension of these toroidal pores. Finally, transmission electron microscopy revealed that melittin formed pores via peptide oligomerization by the toroidal pore-forming mechanism. The toroidal pores composed of 7-8 nm diameter rings that encircled 3.5-4.5 nm diameter cavities on zwitterionic lipid vesicles.
Research Center for Proteineous Materials, Chosun University, Kwangju 501-759, Republic of Korea.
Seong-Cheol
SC
Park
Jin-Young
JY
Kim
Sun-Oh
SO
Shin
Chan-Young
CY
Jeong
Mi-Hyun
MH
Kim
Song Yub
SY
Shin
Gang-Won
GW
Cheong
Yoonkyung
Y
Park
Kyung-Soo
KS
Hahm
D002462:Cell Membrane / Q000737:chemistry; D002473:Cell Wall / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure*; D002686:Chitin / Q000737:chemistry; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000648:ultrastructure; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000648:ultrastructure; D008070:Lipopolysaccharides / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008555:Melitten / Q000737:chemistry* / Q000494:pharmacology*; D046529:Microscopy, Electron, Transmission; D010457:Peptidoglycan / Q000737:chemistry; D016062:Porosity; D015003:Yeasts / Q000187:drug effects / Q000648:ultrastructure
D008070:Lipopolysaccharides; D008081:Liposomes; D010457:Peptidoglycan; D002686:Chitin; D008555:Melitten