Membrane-mediated assembly of annexins studied by site-directed spin labeling.
Annexins are soluble proteins that bind to membranes in the presence of Ca2+. Crystal structures have been determined for some soluble forms, but little is known about the important membrane-bound state. We employed site-directed spin labeling to demonstrate that 1) annexin XII assumes a trimer configuration similar to the crystal structure when bound to bilayers under physiological conditions; 2) trimer assembly on bilayers is remarkably rapid, occurring on a millisecond time scale, whereas subunit exchange requires hours; and 3) different annexins can mix to form heterotrimers. The rapid assembly and heterotrimer formation have important implications concerning the cellular functions of annexins.
Jules Stein Eye Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
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R
Langen
J M
JM
Isas
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H
Luecke
H T
HT
Haigler
W L
WL
Hubbell
D017302:Annexins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D013113:Spin Labels
D017302:Annexins; D013113:Spin Labels