Genetic Requirements for Conjugational Recombination in the Presence of
λ Gam Protein in Escherichia coli

Ivana Ivančić-Bače¹, Nikolina Škrobot¹, Davor Zahradka², Erika Salaj-Šmic² and Krunoslav Brčić-Kostić²*

¹Department of Molecular Biology, Faculty of Natural Sciences, Rooseveltov trg 6, HR-10000 Zagreb, Croatia
²Department of Molecular Genetics, Ruđer Bošković Institute, Bijenička 54, P. O. Box 180, HR-10002 Zagreb, Croatia

Article history:
Received: July 5, 2002
Accepted: November 7, 2002

Key words:
Escherichia coli, phage λ
, conjugational recombination, RecBCD enzyme, Gam protein

Summary:
The Gam protein of phage
λ is a well-known inhibitor of the enzymatic activities of the RecBCD enzyme, the major enzyme involved in homologous recombination in bacteria Escherichia coli. In this work, we studied (i) the effect of the RecA loading-deficient recB (recB^D1080A) mutation on conjugational recombination in the presence of
λ phage Gam protein and (ii) additional genetic requirements for the RecBCD Gam-mediated conjugational recombination. For this purpose, we introduced Gam⁺ and Gam^– expressing plasmids into wild type cells and different mutants of E. coli (recJ, recB^D1080A, recB, recN, recF, recR, recO, recD), and determined the yields of recombinants after Hfr mediated conjugation. The obtained results suggest that RecA loading activity is not inhibited by Gam and that conjugational recombination in the presence of Gam is partially dependent on recJ and recO gene products.

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