TY - JOUR
T1 - Membrane fusion in a model system
T2 - Mucocyst secretion in Tetrahymena
AU - Satir, Birgit
AU - Schooley, Caroline
AU - Satir, Peter
PY - 1973/1/1
Y1 - 1973/1/1
N2 - The freeze-fracture, freeze-etch technique can be employed to reveal new details of the process of fusion of two unit membranes For this study, mucocyst discharge in Tetrahymena pyriformis provides a model system with certain general implications The undischarged mature mucocyst is a saclike, membrane-bound, secretory vesicle containing crystalline material The organelle tip finds its way toward a special site, a rosette of 150 A diameter particles within the plasma membrane. To match this site, the mucocyst membrane forms an annulus of 110 A diameter particles, above whose inner edge the rosette particles sit. Discharge of some mucocysts is triggered by fixation. As discharge proceeds, the organelle becomes spherical and its content changes from crystalline to amorphous. The cytoplasm between the two matching membrane sites is squeezed away and the membranes fuse Steps in membrane reorganization can be reconstructed from changes in rosette appearance in the fracture faces. First, a depression in the rosette-the fusion pocket-forms. The rosette particles spread at the lip as the pocket deepens and enlarges from 60 to 200 nm. The annulus particles then become visible at the lip, indicating completed fusion of the A fracture faces of mucocyst and plasma membranes The remaining B faces of the two membranes have opposite polarities When the content of the mucocyst is released, the edges of these faces join so that the unit membrane runs uninterruptedly around the lip and into the pocket.
AB - The freeze-fracture, freeze-etch technique can be employed to reveal new details of the process of fusion of two unit membranes For this study, mucocyst discharge in Tetrahymena pyriformis provides a model system with certain general implications The undischarged mature mucocyst is a saclike, membrane-bound, secretory vesicle containing crystalline material The organelle tip finds its way toward a special site, a rosette of 150 A diameter particles within the plasma membrane. To match this site, the mucocyst membrane forms an annulus of 110 A diameter particles, above whose inner edge the rosette particles sit. Discharge of some mucocysts is triggered by fixation. As discharge proceeds, the organelle becomes spherical and its content changes from crystalline to amorphous. The cytoplasm between the two matching membrane sites is squeezed away and the membranes fuse Steps in membrane reorganization can be reconstructed from changes in rosette appearance in the fracture faces. First, a depression in the rosette-the fusion pocket-forms. The rosette particles spread at the lip as the pocket deepens and enlarges from 60 to 200 nm. The annulus particles then become visible at the lip, indicating completed fusion of the A fracture faces of mucocyst and plasma membranes The remaining B faces of the two membranes have opposite polarities When the content of the mucocyst is released, the edges of these faces join so that the unit membrane runs uninterruptedly around the lip and into the pocket.
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U2 - 10.1083/jcb.56.1.153
DO - 10.1083/jcb.56.1.153
M3 - Article
C2 - 4629881
AN - SCOPUS:0015535033
SN - 0021-9525
VL - 56
SP - 153
EP - 176
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 1
ER -