title: A DNA polymerase from Ustilago maydis. Evidence of proof-reading by the associated 3' leads to 5' deoxyribonuclease activity.
abstract: The 3' leads to 5' deoxyribonuclease activity associated with an Ustilago maydis DNA polymerase hydrolysed non-complementary 3'-primer termini about 12 times more rapidly than complementary termini. An analysis of its substrate specificity suggested that, although it was unable to hydrolyse fully single-stranded polynucleotides, it could hydrolyse such regions less than about four nucleotides in length covalently bound to a primer molecule which was base-paired to a complementary template strand. Template-primer combinations containing complementary or non-complementary primer termini both supported polynucleotide synthesis, but whereas the former were conserved, the latter were hydrolysed during the reaction thus allowing synthesis to occur. No addition of nucleotides onto a conserved non-complementary 3'-primer terminus was detected. The deoxyribonuclease activity therefore fulfilled a proof-reading function during DNA synthesis in vitro.
mesh_terms: D001487:Basidiomycota / Q000201:enzymology*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000378:metabolism*; D007700:Kinetics; D011089:Polydeoxyribonucleotides; D013329:Structure-Activity Relationship; D013698:Templates, Genetic; D014588:Ustilago / Q000201:enzymology*
chemical_list: D011089:Polydeoxyribonucleotides; D004259:DNA-Directed DNA Polymerase; D003851:Deoxyribonucleases