ABC Excinuclease

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A 260,000 Mr protein complex containing the subunits coded for by the uvrA, uvrB and uvrC genes of E. coli. UvrA is an adenosine triphosphatase and brings into position UvrB, which after attaching to the DNA cuts it at the 3′ position, and that provides the opportunity for UvrC to incise at the 5′ position. UvrD, a helicase releases the damaged oligomer along with UvrC. Following these events, DNA polymerase fills in the correct nucleotides. In yeast, the RAD1, 2, 3, 4, 10, and 14, carry out the same tasks as the ABC excinucleases of bacteria. In humans, the XPA (a damage recognition protein, comparable to UvrA), binds to the XPF-ERCC1 (excision repair cross-complementing protein) heterodimer and to the human single strand binding replication protein, HSSB. XPF (3′ cut) and XPG (5′ cut) are nucleases. The gap-filling polymerases are polδ and polε. XPB and XPD are helicase subunits of the TFIIH transcription factor. The excinuclease complex is released at the end of the process with the ...