Molecular structure of the gap junctional channel

Area of Science:

• Cell biology
• Molecular biology
• Biochemistry

Background:

• Gap junctions are essential for intercellular communication.
• Previous studies identified various proteins in gap junctional preparations, but their specific roles were unclear.

Purpose of the Study:

• To identify and characterize the core protein components of gap junctions.
• To investigate the relationship between different gap junction proteins and their structural contribution.

Main Methods:

• Two-dimensional peptide mapping
• Immunoblotting
• Site-specific antiserum generation
• Immuno-localization studies

Main Results:

• A 16,000 molecular weight (16K) protein was consistently found in all gap junctional isolates, unrelated to the 27K protein.
• The 27K protein and its fragments were absent in trypsin-treated preparations, suggesting it's not integral to the gap junction structure.
• Peptide mapping and immunoblotting revealed that 16K proteins from various species and the arthropod 18K protein form a family of related junctional proteins.
• An antiserum against the N-terminus of the mouse liver 16K protein cross-reacted with all tested 16K and 18K forms, indicating a conserved antigenic determinant.
• Immuno-localization suggested the N-terminus is located on the cytoplasmic side of the gap junction, accessible to digestion.

Conclusions:

• The 16K protein is a fundamental and conserved component of gap junctions across diverse species.
• The 16K and 18K proteins represent a family of related junctional proteins.
• The N-terminus of the 16K protein is a conserved, externally exposed region crucial for identification.