The origin of protein and fatty yolk in Rana pipiens. V. Unusual paracrystalline configurations within the yolk...

Three unusual highly ordered configuration of yolk protein in yolk precursor bodies are described. These differ from the crystalline structure of the main body of mature yolk platelets. One of these is an aggregation of paired membranes wih a spacing of about 100 A between the members of a pair. The paired membranes of such an aggregation may be straight, parallel, and very close together; they may appear as a tight whorl; or they may display an intermediate random arrangement with varying distances between pairs. Another configuration is a tubule with a diameter of about 450 A, whose wall appears in cross section to consist of particles measuring 50 X 100 A. A third configuration is a crystalline array of rows of angular-shaped particles with a spacing of about 160 A. It is suggested that these may represent intermediates in the transition of vitellogenin to lipovitellin and phosvitin.