The structure and function of the replication initiation protein of the drug resistance factor R6K will be studied using biochemical and genetic techniques with the long-term objectives of understanding the initiation step of DNA replication. The initiation of replication is the most important step and perhaps the only step which regulates the orderly replication of genes and, therefore, it has important implications for understanding the control of gene duplication in normal and abnormal or cancerous cells. We have partially purified the replication initiation protein of R6K by tagging it with Beta galactosidase which not only provides a convenient marker but also stabilizes the initiator protein. The tagged initiator has identical DNA-binding and replication initiation activities as the nontagged, original initiator protein. Using the techniques of chemical protection, site specific mutagenesis and missense suppression we aim to study the DNA protein interaction, between the initiator and its binding site and between the initiator and other proteins of the replisome.