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Low molecular weight GTP-binding proteins associated with zymogen granule membranes from rat pancreas

P J Padfield1, J D Jamieson

  • 1Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510.

Biochemical and Biophysical Research Communications
|January 31, 1991
PubMed

Insights

Researchers identified seven low molecular weight GTP-binding proteins in rat pancreatic zymogen granule membranes. These proteins are located on the cytoplasmic side and may play a role in regulated secretion.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Zymogen granules are key organelles in pancreatic acinar cells responsible for storing and secreting digestive enzymes.
  • GTP-binding proteins are known regulators of membrane trafficking and fusion events in eukaryotic cells.

Purpose of the Study:

  • To identify and characterize low molecular weight GTP-binding proteins associated with rat pancreatic zymogen granule membranes.
  • To investigate the localization and membrane association of these GTP-binding proteins.

Main Methods:

  • Proteomic analysis of zymogen granule membranes and cytosolic fractions.
  • Treatment of granules with proteases (trypsin, proteinase K) to assess protein accessibility.
  • Extraction of membrane proteins using high salt, urea, and alkaline carbonate solutions.
  • Phase partitioning in Triton X-114 to determine membrane association.

Main Results:

  • At least seven low molecular weight GTP-binding proteins (21.5–29 kDa) were found associated with zymogen granule membranes.
  • Similar proteins were present in the cytosol but in different proportions.
  • Protease treatment indicated these proteins are on the cytoplasmic face of the granule membrane.
  • Proteins were resistant to extraction by salt, urea, and alkaline carbonate but partitioned into the detergent phase of Triton X-114, indicating tight membrane association.

Conclusions:

  • Low molecular weight GTP-binding proteins are integral components of the pancreatic zymogen granule membrane.
  • Their localization and association suggest a potential role in the regulated secretion process via membrane fusion mechanisms.

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