BIOL308 Lecture Notes - Lecture 11: Dna Polymerase Iii Holoenzyme, Dna Polymerase I, Exonuclease
16 Jul 2014
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Document Summary
Enzyme responsible for synthesis of new dna strands. Some of dna pol i mutants were viable and made dna at nromal rates --> not major enzyme for dna replication in vivo. Dna pol iii - key enzyme - catalyzes synthesis of dna from rna primers. Large complex protein composed of 10 different polypeptides. Core polymerase composed of three subunits; , , . : active site for nucleotide addition in 5"-3" direction. :3"-5" exonuclease [activity that "proof-reads"] removes incorrectly added data. Subunit functions as a clamp; it associates with core at 3" end of the growing strand, increases the processivity of polymerase. The rest of subunits [shared by two core polymerases] Form complex involved in opening and closing of the clamp. Loads subunit onto dna template [atp required] Complex includes two copies of subunit which help dimerization of two core polymerases. 3"-5" is exonuclease activity, the proofreading and removal of mistakes. Dna polymerase 3 haloenzyme has 2 core polymerases.
