2-DIMENSIONAL CRYSTALLIZATION OF AVIDIN ON BIOTINYLATED LIPID MONOLAYERS

Two-dimensional crystals of avidin were obtained on mixed lipid monolayers containing biotinylated lipids (N-biotinyl-dipalmitolyl-L-alpha-phosphatidyl ethanolamine and dioleoyl phosphatidyl choline) by specific interaction. Image analysis of electron micrographs of these crystals revealed p2 symmetry with the unit cell parameters a = 66 +/- 2 Angstrom, b = 68 +/- 1 Angstrom, and gamma = 121 +/- 4 degrees. The projection map showed, at a resolution of about 27 Angstrom, that the four subunits within one avidin molecule are separated into two parts. Comparison between avidin and streptavidin reveals that avidin molecule binds to the lipid monolayer in an orientation similar to that of streptavidin.