Electron microscopy and image analysis of the GroEL-like protein and its complexes with glutamine synthetase from pea leaves.

The molecular structure of GroEL-like protein from pea leaves has been studied by electron microscopy and image analysis of negatively stained particles. Over 1500 molecular projections were selected and classified by multivariate statistical analysis. It was shown that the molecule consists of 14 subunits arranged in two layers with 72 point group symmetry. Side view projections of the molecule show a four-striation appearance, which subdivides both layers of seven subunits into two halves; this may be explained by a two-domain structure of the subunits. The presence in protein preparations of projections corresponding to one layer of subunits or half-molecules is consistent with the molecular structure suggested. Electron microscopic evidence for a specific association of GroEL-like protein and octameric glutamine synthetase, which was co-purified with this protein, was obtained.