|
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, 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). ==Research== Because the 5' → 3' exonuclease activity of DNA polymerase I from ''E. coli'' makes it unsuitable for many applications, the Klenow fragment, which lacks this activity, can be very useful in research. The Klenow fragment is extremely useful for research-based tasks such as: * Synthesis of double-stranded DNA from single-stranded templates * Filling in receded 3' ends of DNA fragments to make 5' overhang blunt * Digesting away protruding 3' overhangs * Preparation of radioactive DNA probes The Klenow fragment was also the original enzyme used for greatly amplifying segments of DNA in the polymerase chain reaction (PCR) process, before being replaced by thermostable enzymes such as Taq polymerase. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Klenow fragment」の詳細全文を読む スポンサード リンク
|