RPA1_DBD_C: A subfamily of OB folds corresponding to the C-terminal OB fold, the ssDNA-binding domain (DBD)-C, of human RPA1 (also called RPA70). RPA1 is the large subunit of Replication protein A (RPA). RPA is a nuclear ssDNA-binding protein (SSB) which appears to be involved in all aspects of DNA metabolism including replication, recombination, and repair. RPA also mediates specific interactions of various nuclear proteins. In animals, plants, and fungi, RPA is a heterotrimer with subunits of 70KDa (RPA1), 32kDa (RPA2), and 14 KDa (RPA3). In addition to DBD-C, RPA1 contains three other OB folds: DBD-A, DBD-B, and RPA1N. The major DNA binding activity of RPA is associated with RPA1 DBD-A and DBD-B. RPA1 DBD-C is involved in DNA binding and trimerization. It contains two structural insertions not found to date in other OB-folds: a zinc ribbon and a three-helix bundle. RPA1 DBD-C also contains a Cys4-type zinc-binding motif, which plays a role in the ssDNA binding function of this domain. It appears that zinc itself may not be required for ssDNA binding.
Structure:1L1O_DEF; Human RPA trimerization core interface; defined at 3.5A contacts between subunits in the heterotrimer.
Comment:The RPA trimerization core consists of DBD-D (the central DNA-binding domain of RPA2), DBD-C (the C-terminal DNA-binding domain of RPA1), and intact RPA3. Each contains an OB-fold domain flanked by a helix at the C-terminus, which mediate trimerization.
Jiyao W et al.(2023). "The conserved domain database in 2023.",