The role for zinc in replication protein A.
Heterotrimeric human single-stranded DNA (ssDNA)-binding protein, replication protein A ( RPA), is a central player in DNA replication, recombination, and repair. The C terminus of the largest subunit, RPA70, contains a putative zinc-binding motif and is implicated in complex formation with two smaller subunits, RPA14 and RPA32. The C-terminal domain of RPA70 (RPA70- CTD) was characterized using proteolysis and x-ray fluorescence emission spectroscopy. The proteolytic core of this domain comprised amino acids 432-616. X-ray fluorescence spectra revealed that RPA70- CTD possesses a coordinated Zn(II). The trimeric complex of RPA70- CTD, the ssDNA-binding domain of RPA32 (amino acids 43-171), and RPA14 had strong DNA binding activity. When properly coordinated with zinc, the trimer's affinity to ssDNA was only 3-10-fold less than that of the ssDNA-binding domain in the middle of RPA70. However, the DNA-binding activity of the trimer was dramatically reduced in the presence of chelating agents. Our data indicate that (i) Zn(II) is essential to stabilize the tertiary structure of RPA70- CTD; (ii) RPA70- CTD possesses DNA-binding activity, which is modulated by Zn(II); and (iii) ssDNA binding by the trimer is a synergistic effect generated by the RPA70- CTD and RPA32.[1]References
- The role for zinc in replication protein A. Bochkareva, E., Korolev, S., Bochkarev, A. J. Biol. Chem. (2000) [Pubmed]
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