Structural Analysis of Stained and Unstained Two-Dimensional Ribosome Crystals

Abstract

The Italian lizaid, Lacerta sicula, develops large ery stalline sheets of ribosomes during hibernation [1]. The sheets form on the endoplasmic reticulum membrane of previtellogenic oocytes and tend to aggregate into Clusters measuring 10–20 μm across [2]. Thin sections through the clusters show each sheet to be composed of two layers of ribosomes. These double layers are lined on either side with endoplasmic reticulum membranes (Fig. 1a). Sections cut through sheets at an oblique angle show that each layer represents a two-dimensional crystal of ribosome tetramers arranged on a square lattice (Fig. 1b). The space group of the two-dimensional crystals is P4, the until cell dimensions is 595 Å. Both layers have the same symmetry but face in opposite directions so that they appear to b of opposite hand in sections. It can be shown that the layer against the membrane always has the configuration shown in Fig. 2 when seen from above (from here on referred to as “right-handed” configuration [3, 4].)