A TRUNCATED FORM OF THE BACTERIOPHAGE-MU-B PROTEIN PROMOTES CONSERVATIVE INTEGRATION, BUT NOT REPLICATIVE TRANSPOSITION, OF MU-DNA

The phage-encoded proteins required for conservative integration of infecting bacteriophage Mu DNA were investigated. Functional gpA, an essential component of the phage transposition system, is required for integration. The Mu B protein, which greatly enhances replicative transposition of Mu DNA, is also required. A truncated form of gpB lacking 18 amino acids from the carboxy terminus is blocked in replicative transposition, but not conservative integration. Results point to a more prominent role for gpB than simply a replication enhancer in Mu DNA transposition. The ability of a truncated form of B to function in conservative integration, but not replicative transposition, also suggests a key role for the carboxy-terminal domain of the protein in the replicative reaction. The existence of a shortened form of gpB, which uncouples conservative integration from replicative transposition, should be invaluable for future dissection of Mu DNA transposition.