Gasser, Kenneth W.
B.S. (Bachelor of Science)
Department of Biological Sciences
Rat pancreatic zymogen granules were studied to assess their role in exocytotic fusion. The granules were isolated by nitrogen cavitation and Percoll density gradient centrifugation. Apical membranes were isolated from the homogenate by a step- gradient and differential centrifugation. Both samples were then checked for purity via marker enzyme assays. Integral proteins were extracted with Triton-X114. Both membrane proteins and isolated integral membrane proteins were characterized by SDS gel electrophoresis. The results showed six candidate fusion proteins of molecular weight 64.1, 61.7, 56.8, 43.1, 42.1, and 14.8 kDal based on their relative hydrophobicity. Membrane fusogenicity was assessed by monitoring the solubilization of the condensed granule core. Vesicle membranes lack the ability to fuse to one another, but will fuse to the apical plasma membrane. However, on a sample to sample basis, the rate of fusion was not correlated to the absolute concentration of apical plasma membrane. Therefore, apical membrane is apparently required for fusion but it does not control the overall rate. The fusion rate may be regulated by the membrane lipid environemnt as shown by an increase in fusion capacity after arachidonic acid treatment of the apical membrane. However, arachidonic acid did not influence the rate when the vesicular membrane was treated. This points toward an integral membrane protein acting as a docking site for the vesicle with fusion rate possibly being controlled by phospholipase and apical plasma membrane fluidity.
Kaufman, Gary, "Characterization of secretory membranes and exocytotic fusion" (1992). Honors Capstones. 280.
23 unnumbered pages
Northern Illinois University
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