Abstract
All thermophilic and hyperthermophilic archaea encode homologs of dimeric Alba (Sac10b) proteins that bind cooperatively at high density to DNA. Here, we report the 2.0 Å resolution crystal structure of an Alba2 (Ape10b2)-dsDNA complex from Aeropyrum pernix K1. A rectangular tube-like structure encompassing duplex DNA reveals the positively charged residues in the monomer-monomer interface of each dimer packing on either side of the bound dsDNA in successive minor grooves. The extended hairpin loop connecting strands β3 and β4 undergoes significant conformational changes upon DNA binding to accommodate the other Alba2 dimer during oligomerization. Mutational analysis of key interacting residues confirmed the specificity of Alba2-dsDNA interactions.
Highlights
Alba is a dimeric, highly basic archaeal chromatin protein
The extended hairpin loop connecting strands 3 and 4 undergoes significant conformational changes upon DNA binding to accommodate the other Alba2 dimer during oligomerization
Overall Structure of Alba2-DNA Complex—On the basis of our earlier work [12], we crystallized Alba2 with 16-bp duplex DNA and collected a data set to 2.0 Å resolution under space group P212121
Summary
Highly basic archaeal chromatin protein. Results: The crystal structure of the Alba2-dsDNA complex was determined. A rectangular tube-like structure encompassing duplex DNA reveals the positively charged residues in the monomer-monomer interface of each dimer packing on either side of the bound dsDNA in successive minor grooves. The overall complex structure reveals a discrete mode of DNA binding, with the positively charged residues on the monomermonomer interface of each dimer packing on either side of the bound dsDNA in successive minor grooves.
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