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.
Park
Seong-Cheol
SC
Research Center for Proteineous Materials, Chosun University, Kwangju 501-759, Republic of Korea.
Kim
Jin-Young
JY
Shin
Sun-Oh
SO
Jeong
Chan-Young
CY
Kim
Mi-Hyun
MH
Shin
Song Yub
SY
Cheong
Gang-Won
GW
Park
Yoonkyung
Y
Hahm
Kyung-Soo
KS
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