Cross-linking of porin with glutardialdehyde: a test for the adequacy of premises of cross-linking theory.
Exposure of porin from Escherichia coli to glutardialdehyde followed by SDS-gel electrophoresis in 3% polyacrylamide yielded three bands that were identified in order of decreasing mobility as monomers and two and three cross-linked polypeptide chains. The distribution of protein among the three species for different extents of reaction showed a remarkably good agreement with corresponding values predicted from cross linking theory for an oligomer composed of three identical subunits arranged according to a 3-fold rotation axis. Electrophoresis performed in 7.5% polyacrylamide yielded four bands that were assigned to polypeptide chain monomers, dimers, and two types of trimers carrying two and three intersubunit cross-links. Our findings provide evidence that the central premise of cross-linking theory, viz. that the intersubunit cross-links formed upon exposure of a protein to a bifunctional reagent be governed by the symmetry of the molecule, is valid. Careful interpretation of cross-linking experiments thus proves an effective method to assess the oligomeric structure of a protein and reveal the symmetry underlying the spatial arrangement of the subunits within the molecule.
Azem
A
A
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Shaked
I
I
Rosenbusch
J P
JP
Daniel
E
E
D003432:Cross-Linking Reagents / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000737:chemistry; D005976:Glutaral / Q000737:chemistry*; D008433:Mathematics; D018272:Porins / Q000737:chemistry* / Q000302:isolation & purification
D003432:Cross-Linking Reagents; D018272:Porins; D005976:Glutaral