Abstract
The T4 ultraviolet endonuclease was previously shown to produce strand incisions (nicks) in ultraviolet-irradiated DNA on the 5' side of thymine dimers. The present studies demonstrate that the purified endonuclease creates 3'-OH and 5'-P termini at the sites of nicking. Photoreactivation of ultraviolet-sensitive sites, thereby demonstrating directly endonucleause has a molecular weight of approximately 18,000 and attacks ultraviolet-irradiated single-stranded Escherichia coli and M-13 DNA.
Highlights
T4 ultraviolet endonuclease was determined from a standard curve constructed from the RF of the marker proteins run in different wells of the same gel
I’hage T7 DNA was ultravioletirradiated at a fluence of 40 J per m2. This DNA was incubated in the presence and absence of Escherichia coli photoreactivating enzyme and the thymine dimer content of an aliquot of each was determined
The rest of the DNA was incubated with T4 ultraviolet endonuclease and sedimented in alkaline sucrose density gradients
Summary
The T4 ultraviolet endonuclease was previously shown to produce single strand incisions (nicks) in ultraviolet-irradiated DNA on the 5’ side of thymine dimers. The present studies demonstrate that the purified endonuclease creates 3’-OH and 5’-P termini at the sites of nicking. The endonuclease has a molecular weight of approximately 18,000 and attacks ultraviolet-irradiated single-stranded Escherichia coli and M-13 DNA. Purified E. coli photoreactivating enzyme (Fraction 111, Method I, Ref. 12) was a gift from Dr Betsy Sutherland, University of California, Irvine. We present evidence that pyrimidine dimers are recognized as substrate sites by the enzyme in single-stranded DNA. Unlabeled and 8H-labeled T7 DNA were prepared by the procedure of Thomas and Abelson [13] from purified phage T7 grown on E. coli B-3 (thy). G-75 from Pharmacia, and acrylamide and N, N’-methylenebisacrylamide (electrophoresis grade) from Aldrich Chemical Co., Inc
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
