Klenow fragment

Functional domains in the Klenow Fragment (left) and DNA Polymerase I (PDB).

The Klenow fragment is a large protein fragment produced when DNA polymerase I from E. coli is enzymatically cleaved by the protease subtilisin. First reported in 1970,[1] it retains the 5' → 3' polymerase activity and the 3’ → 5’ exonuclease activity for removal of precoding nucleotides and proofreading, but loses its 5' → 3' exonuclease activity.

The other smaller fragment formed when DNA polymerase I from E. coli is cleaved by subtilisin retains the 5' → 3' exonuclease activity but does not have the other two activities exhibited by the Klenow fragment (i.e. 5' → 3' polymerase activity, and 3' → 5' exonuclease activity).

  1. ^ Klenow H and Henningsen I (1970). "Selective Elimination of the Exonuclease Activity of the Deoxyribonucleic Acid Polymerase from Escherichia coli B by Limited Proteolysis". Proc. Natl. Acad. Sci. USA. 65 (1): 168–175. Bibcode:1970PNAS...65..168K. doi:10.1073/pnas.65.1.168. PMC 286206. PMID 4905667.