Assembly of clathrin molecules on liposome membranes: a possible event necessary for induction of membrane fusion.
Below pH6, clathrin induces fusion of liposomes containing phosphatidylserine (PS) [Maezawa et al. (1989) Biochemistry 28, 1422-1428]. Under similar conditions clathrin forms self-aggregates, suggesting that the associated form of clathrin may be involved in the fusion process. For examination of this possibility, the extent of fluorescence energy transfer from N-(p-(2-benzimidazolyl)phenyl)maleimide (BIPM)-labeled clathrin to N-(7-dimethyl-amino-4-methyl-3-coumarinyl)maleimide (DACM)-labeled clathrin in the presence of liposomes and the number of binding sites for clathrin in one liposome were examined in the pH region inducing membrane fusion. A high degree of transfer was observed, and the area on the membrane surface occupied by a clathrin molecule was estimated to be much less than that expected from its size, indicating that clathrin binds to the liposome membrane as an associated form, which may be essential for induction of membrane fusion.
Maezawa
S
S
Institute for Enzyme Research, University of Tokushima, Japan.
Yoshimura
T
T
D000818:Animals; D001921:Brain / Q000378:metabolism; D002417:Cattle; D002966:Clathrin / Q000302:isolation & purification / Q000378:metabolism*; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism; D005456:Fluorescent Dyes; D008081:Liposomes / Q000378:metabolism*; D008561:Membrane Fusion; D010713:Phosphatidylcholines / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D002966:Clathrin; D005456:Fluorescent Dyes; D008081:Liposomes; D010713:Phosphatidylcholines; D010718:Phosphatidylserines