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Unformatted text preview: uclease 2. MTHF transfers this
photoexcitation to FADH
3. FADH transfers an electron to
the dimer, breaking the dimer into
thymine monomers, then takes
the electron back. Note the baseipping mechanism of the enzyme!
MHTF = methenyltetrahydrofolate Unfortunately, we (humans) don’t have photolyase! PDB # 1TEZ 7 8 Nucleotide excision repair DNA mismatch repair (in E. coli; humans lack MutH) Xeroderma pigmentosum
- genetic diseases of excision repair.
In humans NER utilizes 16 di erent
proteins. Mutations in many of
these cause XP. = ABC excinuclease Xeroderma pigmentosum (XP) is characterized by sun
sensitivity (severe sunburn with blistering, persistent
erythema on minimal sun exposure, marked freckle-like
pigmentation of the face before age two years), ocular
involvement (photophobia, keratitis, atrophy of the skin of
the lids), and a greatly increased risk of cutaneous neoplasms
(basal cell carcinoma, squamous cell carcinoma, melanoma).
Approximately 25% of a ected individuals have neurologic
manifestations (acquired microcephaly, diminished or absent
deep tendon stretch re exes, progressive sensorineural
hearing loss, and progressive cognitive impairme...
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- Spring '14