A single-stranded DNA binding protein from Drosophila melanogaster: characterization of the heterotrimeric protein and its interaction with single-stranded DNA.


We describe the purification to near homogeneity of a single-stranded ...
We describe the purification to near homogeneity of a single-stranded DNA binding protein from 0-18-h embryos of Drosophila melanogaster. Drosophila SSB (D-SSB) is a heterotrimer with subunits of molecular weight of 70,000, 30,000, and 8000. It has a Stokes radius of 48.6 +/- 2 A and s20,w = 5.0 +/- 0.2 S. The interaction of D-SSB with ssDNA was examined by the quenching of intrinsic protein fluorescence. The binding site size was determined to be n = 22 +/- 4 nucleotides with a maximum quenching Qm = 35 +/- 3%. Equilibrium titrations indicate that D-SSB binds with low cooperativity, omega = 10-300, and high apparent affinity, K omega = (0.7-5) x 10(7) M-1, at 225 mM NaCl. Sedimentation of D-SSB bound to small oligonucleotides demonstrates that D-SSB does not require protein association for binding. D-SSB stimulates the extent and processivity of DNA synthesis of its cognate DNA polymerase alpha. On the basis of these properties, we conclude that D-SSB is the Drosophila cognate of the human and yeast SSB/RP-A proteins.




new topics/pols set partial results complete validated


No results available for this paper.

Entry validated by:

Using Polbase tables:


Tables may be sorted by clicking on any of the column titles. A second click reverses the sort order. <Ctrl> + click on the column titles to sort by more than one column (e.g. family then name).


It is also possible to filter the table by typing into the search box above the table. This will instantly hide lines from the table that do not contain your search text.