The principal goal of this research project is the determination of the crystal structure of a development specific protein (Protein S) from the bacterial species, myxococcus xanthus. This bacterial species is unique among bacteria in its capacity for multicellular development; which consists of an aggregation and formation of multicellular fruiting bodies. Protein S, synthesized during this stage is essential for the aggregation and self assembly of the fruiting body. This assembly is regulated by calcium ions. On treatment with trypsin, a resistant core peptide is produced which competes with the intact protein S in self assembly around the spore surface. Crystals of Protein S in the presence of Ca++ have already been grown and found to give diffraction pattern to atomic resolution. Crystals of the protein will be grown in the total absence of any metal ions. Crystals of the core protein will also be prepared for structure analysis by the X-ray diffraction technique. The structures of Protein S, in the prsence and in the absence of calcium ions and the structure of the core protein will be used to understand the process and regulation of the assembly of the Protein S in the fruiting bodies of the myxobacteria.