Self-Association of Gene-32 Protein of Bacteriophage T4

The self-association of gene-32 protein has been studied by sedimentation equilibrium centrifugation and polyacrylamide gel electrophoresis, in order to better understand its role in DNA replication and genetic recombination. The monomer molecular weight of gene-32 protein is 38,000 in guanidine hydrochloride and 34,000 in sodium dodecyl sulfate, in agreement with the results of Alberts and coworkers. Stable dimers of gene-32 protein occur under various conditions, among which are high ionic strength and pH 10. The occurrence of stable dimers under some conditions and higher aggregates under others indicates there are two types of protein-protein interactions occurring in gene-32 protein self-association. The association that occurs above about 0.1 mg/ml concentration of protein produces at least decamers.A model for the DNA replication fork is postulated that requires the two different interactions that occur in gene-32 protein aggregation. In the model, gene-32 protein holds the two strands of the DNA duplex in a conformation that prevents their reannealing and, therefore, facilitates replication and recombination.