engleski

SSB protein from antibiotic-producing bacteria

Streptomyces species are filamentous soil bacteria the best known for their production of a variety types of antibiotics. The crystal structure of the single-stranded DNA-binding protein (SSB) from Streptomyces coelicolor has been solved recently. These proteins have essential role in cell propagation and survival. They are involved in DNA recombination, replication and repair. SSB from S. coelicolor possesses a common conserved central OB fold found in all structurally determined SSB proteins. However, it shows variations previously found in quaternary structure only in mycobacterial SSBs. The strand involved in the clamp mechanism characteristic of this type of quaternary structure leads to higher stability of the homotetramer and this 3D-structure is predicted to be the most stable among structurally characterized bacterial or human mitohondrial SSBs. SSBs also possess conserved C-terminal domain which has role in interacting with other proteins and in many cases this interaction stimulates its biochemical activities. It has been shown that SSB protein from Escherichia coli interacts with at least 14 different proteins. There are no data on interactions of the S. coelicolor SSB with other cell proteins. TAP (tandem affinity purification) technology has been used to purify SSB and its interacting partner proteins. Sequences coding for two tags (protein A and Calmodulin binding peptide, CBP) separated with TEV protease cleavage site have been cloned on 5' terminus of ssb gene. Such construct was further subcloned into S. coelicolor and the cell extract from the exponential phase of growth and two affinity columns were used to purify SSB and its interacting protein-partners. Eluted proteins were further separated with preparative SDS-PAGE, analyzed by mass spectrometry and the obtained results will be presented.

SSB; tandem affinity chromatography; Streptomyces ceolicolor

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