Genetic analysis of recC73 suppressor mutation mutant in Escherichia coli

Sumpor, Danijel (2013) Genetic analysis of recC73 suppressor mutation mutant in Escherichia coli. Diploma thesis, Faculty of Science > Department of Biology.

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Abstract

In Escherichia coli, RecBCD is responsible for performing a number of functions that include the DNA metabolism. The enzyme is composed of three subunits called RecB, RecD and RecC which together form a holoenzyme RecBCD. Each subunit has its own specific role, based on which enzyme as a whole can act as helicase and nuclease, and have the ability to recognize Chi sites within DNA sequences. Numerous mutants of RecBCD have been discovered, and depending on site of the mutation, roles of the enzyme can be altered in some or all of the activities that the enzyme performs. Mutant recC73 belongs to the so-called null mutants for it is recombination deficient, has no nuclease activity and cannot identify the location of Chi (Rec- Chi- Nuc-). Mutation recC73 is discovered to represent a deletion of T at the 1938 position within gene recC, causing a synthesis of several erroneous amino acids and premature termination of translation and synthesis of a truncated protein RecC73. Suppressor mutation, which is found in the promoter region of the gene is an "improving" mutation that causes increased transcription of the gene and an increased amount of protein RecC73. This work represents the genetic analysis of suppressor mutation in mutant recC73. By using qRT-PCR method, we showed that a certain amount of gene transcripts of recC in a suppressed mutant recC73 was increased when compared to the original mutant recC73. By overexpression of alleles recC73 from plasmids we achieved suppression of recC null mutations similar to the promoter mutation, whereas the effect of suppressing mutation recC73 through overexpression of genes recB or recD from plasmids has not been established. The results showed positive effect of suppression and the importance of the RecC subunit in the RecBCD assembly.

Item Type: Thesis (Diploma thesis)
Keywords: RecBCD, recC73, homologous recombination, Escherichia coli
Supervisor: Ivančić Baće, Ivana
Co-supervisor: Majsec, Kristina
Date: 2013
Number of Pages: 38
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 25 Sep 2014 11:59
Last Modified: 25 Sep 2014 11:59
URI: http://digre.pmf.unizg.hr/id/eprint/2825

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