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CST, complex subunit STN1, C terminal STN1 is a component of the CST complex, a complex that binds to single-stranded DNA and is required for protecting telomeres from DNA degradation. The CST complex binds single-stranded DNA with high affinity in a sequence-independent manner, while isolated subunits bind DNA with low affinity on their own. In addition to telomere protection, the CST complex probably has a more general role in DNA metabolism at non-telomeric sites. This entry represents the C-terminal region of Stn1 which has two winged helix-turn-helix (wHTH) motifs, wHTH1 and wHTH2. wHTH1 is structurally similar to that in RPA32 with a large insertion between helices alpha2 and alpha3, unique to Stn1, that may allow interaction with a different set of proteins that function at telomeres such as Ctc1. wHTH2 is most similar to the DNA-binding wHTH motifs of the pur operon repressor and RepE replication initiator, but it does not bind double-stranded DNA.
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