The T-even bacteriophage - E. coli system will be investigated as a model system of viral invasion, viral structure and viral assembly. Recent results have been identified a number of phage genes which produce a set of enzymes which ultimately form a unique type of folic acid - a dihydropteroyl hexaglutamate. In addition these enzymes have been found to be structural components of the central hub of the tail baseplate of the phage particle. Work will be devoted to determine: 1) The pathway or sequence of the phage gene products take to assemble the central baseplate hub; 2) The nature of the interaction of these hub components with each other during the formation of phage-induced folate; 3) Development of new methods to determine the assembly sequence pathway including the use of inhibitors to accumulate intermediates and selective labeling of different hub components. 4) The nature of the interaction of the hub components with host cell membrane. 5) The nature of the interaction of these hub components with the tail fibers especially the interaction of T4 gene product 28 with the zinc-containing short tail fiber. It is hoped that the detailed chemical knowledge gained from these studies will lead to the control of virus assembly and to new principles involving assembly of other viruses including those causing human diseases.