Locations of functional domains in the RecA protein. Overlap of domains and regulation of activities

Abstract

We review the locations of various functional domains of the RecA protein of Escherichia coli, including how they have been assigned, and discuss the potential regulatory roles of spatial overlap between different domains. RecA is a multifunctional and ubiquitous protein involved both in general genetic recombination and in DNA repair: it regulates the synthesis and activity of DNA repair enzymes (SOS induction) and catalyses homologous recombination and mutagenesis. For these activities RecA interacts with a nucleotide cofactor, single-stranded and double-stranded DNAs, the LexA repressor, UmuD protein, the UmuD'2C complex as well as with RecA itself in forming the catalytically active nucleofilament. Attempts to locate the respective interaction sites have been advanced in order to understand the various functions of RecA. An intriguing question is how these numerous functional sites are contained within this rather small protein (38 kDa). To assess more clearly the roles of the respective sites and to what extent the sites may be interacting with each other, we review and compare the results obtained from various biological, biochemical and physico-chemical approaches. From a three-dimensional model it is concluded that all sites are concentrated to one part of the protein. As a consequence there are significant overlaps between the sites and it is speculated that corresponding interactions may play important roles in regulating RecA activities.