The telomeric protein Pot1 from Schizosaccharomyces pombe binds ssDNA in two modes with differing 3' end availability.
Bottom Line: These experiments reveal one binding mode characterized by only subtle alternations to the individual OB-fold subdomain structures, resulting in an inaccessible 3' end of the ssDNA.The second binding mode, which has equivalent affinity, interacts differently with the 3' end, rendering it available for interaction with other proteins.These findings suggest a structural switch that contributes to telomere end-protection and length regulation.
Affiliation: Department of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309, USA.Show MeSH
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Mentions: At lower concentrations (34 μM), Pot1-DBD+12mer and Pot1-DBD+15mer elute with molar masses of ∼45–50 kDa, similar to the predicted molecular weights of 43.2 and 44.1 kDa for the 1:1 Pot1-DBD+12mer and 1:1 Pot1-DBD+15mer complexes, respectively (Figure 3A). Pot1-DBD+15mer elutes as a uniform peak, while Pot1-DBD+12mer elutes as a broad peak, suggesting the presence of multiple conformations or complexes in the presence of 12mer. Despite this mixture of species, the 1:1 complex appears to be far more prevalent than the 2:1 complex based on the calculated molar mass.
Affiliation: Department of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309, USA.