該基因編碼異三聚體復制蛋白A（RPA）復合物的最大亞單位，與單鏈DNA（SSDNA）結合，形成核蛋白復合物，在DNA代謝中起重要作用，參與DNA復制、修復、重組、端粒維持，并通過激活共濟失調毛細血管擴張癥和RAD3相關蛋白（ATR）激酶來協調細胞對DNA損傷的反應。核蛋白復合物保護單鏈dna免受核酸酶的侵害，防止形成干擾修復的二級結構，并協調不同基因組維持因子的募集和離開。該亞單位包含四個寡核苷酸/寡糖結合（ob）結構域，盡管大多數ssdna結合發生在其中兩個結構域中。異三聚體復合物具有兩種不同的ssdna結合模式：低親和力和高親和力，這兩種模式決定了ssdna結合域的利用。不同的結合方式在dna結合的長度和與之相互作用的蛋白質上不同，從而在調控不同的基因組維持途徑中發揮作用。[由RefSeq提供，2017年9月]
This gene encodes the largest subunit of the heterotrimeric Replication Protein A (RPA) complex, which binds to single-stranded DNA (ssDNA), forming a nucleoprotein complex that plays an important role in DNA metabolism, being involved in DNA replication, repair, recombination, telomere maintenance, and co-ordinating the cellular response to DNA damage through activation of the ataxia telangiectasia and Rad3-related protein (ATR) kinase. The nucleoprotein complex protects the single-stranded DNA from nucleases, prevents formation of secondary structures that would interfere with repair, and co-ordinates the recruitment and departure of different genome maintenance factors. This subunit contains four oligonucleotide/oligosaccharide-binding (OB) domains, though the majority of ssDNA binding occurs in two of these domains. The heterotrimeric complex has two different modes of ssDNA binding, a low-affinity and high-affinity mode, determined by which ssDNA binding domains are utilized. The different binding modes differ in the length of DNA bound and in the proteins with which it interacts, thereby playing a role in regulating different genomic maintenance pathways. [provided by RefSeq, Sep 2017]