Plasmid DNA Primases and their Role in Bacterial Conjugation
RNA primers necessary for starting DNA chain growth are generally made by the transcriptional activity of a group of enzymes called DNA primases. The primase of Escherichia coli is the 60,000 dalton (60 kd) product of the dnaG gene, which functions to generate primers for discontinuous replication of the bacterial chromosome and of at least some plasmids, as well as for complementary strand- synthesis on certain single-stranded genomes (24). Recently a variety of conjugative plasmids have been shown to encode DNA primases active in an assay requiring primer synthesis on single-stranded phage fd DNA. The list includes members of the B, C, I1. (= Iα), I1+B, I2, K, M, P, and U incompatibility groups (44). Representative plasmids of most of the other groups, including F, have been screened in this assay and are currently classified as primase negative (26), but it is possible that some may specify DNA primases that are unable to use fd DNA as a template. In this article, which concentrates on the primases specified by ColIb-P9 (IncI1), RP4 (IncP), and R16 (IncB), we review the biochemistry of these enzymes and the organization of the appropriate structural genes, and discuss the physiological role of their products in plasmid DNA metabolism during bacterial conjugation.
KeywordsRecombination Polypeptide Pyrimidine Purine Rifampicin
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- 4.Barth, P.T., and N.J. Grinter (1983) A possible site-specific recombination and resolution system in plasmid RP4. J. Cell. Biochem. Suppl. 7B Abstract 0891, p. 149.Google Scholar
- 6.Barth, P.T., L. Tobin, and G.S. Sharpe (1981) Development of broad host-range plasmid vectors. In Molecular Biology, Pathogenicity and Ecology of Bacterial Plasmids, S.B. Levy, R.C. Clowes, and E.L. Koenig, eds. Plenum Press, New York, pp. 439–448.Google Scholar
- 12.Coetzee, J.N., D.E. Bradley, and R.W. Hedges (1982) Phages la and I2-2: IncI plasmid-dependent bacteriophages. J. Gen. Microb. 128: 2797–2804.Google Scholar
- 13.Curtiss, III, R., and R.G. Fenwick, Jr. (1975) Mechanism of conjugal plasmid transfer. In Microbiology — 1974, D. Schlessinger, ed. American Society for Microbiology, Washington, D.C., pp. 156–165.Google Scholar
- 14.Dalrymple, B.P. (1982) Plasmid encoded DNA primases. Ph.D. thesis, University of Leicester, England.Google Scholar
- 20.Gilbert, W., and D. Dressier (1968) DNA replication: The rolling circle model. Cold Spring Harbor Symposia on Quantitative Biology. Cold Spring Harbor, New York 33: 473–484.Google Scholar
- 23.Jacob, A.E., J.A. Shapiro, L. Yamamoto, D.I. Smith, S.N. Cohen, and D. Berg (1977) Plasmids studied in Escherichia coli and other enteric bacteria. In DNA insertion elements, plasmids, and episomes, A.I. Bukhari, J.A. Shapiro, and S.L. Adhya, eds. Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y., pp. 607–638.Google Scholar
- 24.Kornberg, A. (1980) DNA replication. W.H. Freeman and Co., San Francisco.Google Scholar
- 25.Kornberg, A. (1982) 1982 Supplement to DNA replication. W.H. Freeman and Co., San Francisco.Google Scholar
- 26.Lanka, E., and P.T. Barth (1981) Plasmid RP4 specifies a deoxyribonucleic acid primase involved in its conjugal transfer and maintenance. J. Bact. 148: 769–781.Google Scholar
- 26a.Lanka, E., and J.P. Fttrste (1984) Function and properties of RP4 DNA primase. In Proteins involved in DNA replication, U. Htibscher and S. Spadari, eds. Plenum Press, New York and London, pp. 265–280.Google Scholar
- 31.Meyer, R., and D.R. Helinski (1977) Unidirectional replication of the P-group plasmid RK2. Biochim. et Biophys. Acta 478: 109–113.Google Scholar