Portal de Periódicos da CAPES

Association of the Prophage P1 ban Protein with the dnaB Protein of Escherichia coli

1979; Wiley; Volume: 94; Issue: 2 Linguagem: Inglês

10.1111/j.1432-1033.1979.tb12910.x

1432-1033

C. Edelbluth, Erich Lanka, Wilhelm von der Hude, M. Mikolajczyk, Heinz Georg Schuster,

RNA and protein synthesis mechanisms

The constitutive synthesis of the dnaB analog ( ban ) protein by prophage P1 bac permitted the construction of an otherwise non‐viable Escherichia coli strain bearing the unsuppressed ( sup − ) amber mutation dnaB 266. Growth of this strain is cryosensitive and the ban protein furnished by prophage P1 bac does not support bacteriophage λ replication [D'Ari et al., J. Mol. Biol. 94 , 341–366 (1975)]. Recently a P1 bac crr prophage mutant was isolated with the ability to confer cryoresistant ( crr ) growth to E. coli sup + dnaB 266. The presence of prophage P1 bac crr in E. coli sup − dnaB 266 makes the strain permissive for λ growth [D. Touati‐Schwartz (1978) in DNA Synthesis‐Present and Future (Molineux, I. & Kohiyama, M., eds) pp. 683–692, Plenum Press, New York. P1 ban protein is isolated by means of a dnaB ‐complementation assay from P1 bac crr lysogens of four E. coli mutants containing either thermo‐sensitive or thermo‐resistant dnaB protein. Monomers of the phage protein ( ban ) are found to be associated with monomers of the host dnaB protein in the form of heteromultimers as was reported earlier for P1 bac lysogens [Lanka et al., J. Biol. Chem. 253 , 4746–4753 (1978)]. The ban protein is, however, overproduced by P1 bac crr when compared to the corresponding P1 bac prophage. Overproduction of ban protein results in a thermoresistance of DNA synthesis in crude cell extracts and thermo‐resistant heteromultimers composed of ban and thermo‐sensitive dnaB subunits. The overproduction of ban protein is also demonstrated in the P1 bac crr lysogen of E. coli sup + dnaB 266 by precipitation with dnaB antibody. The results suggest that cryosensitive growth of E. coli sup + dnaB 266 (P1 bac ) and its inability to support λ replication is due to a cellular deficiency in ban protein molecules rather than to an inefficacy of ban in the absence of an effective dnaB protein.