Question

Cell Biology Short Answer Question: Highlight the differences between different types of restriction endonucleases.

Answer 1

Restriction endonucleases are classified into four groups (Types I, II III, and IV) based on their composition and enzyme cofactor, the nature of their target sequence, and the position of their DNA cleavage site relative to the target sequence.

The major differences are

• Type I enzymes: They  cleave at sites remote from a recognition site and require both ATP and S-adenosyl-L-methionine and it a multifunctional protein with both restriction and methylase characters.
• Type II enzymes very important enzymes are using in rDNA technology and specifically cleave within or at short specific distances from a recognition site and they require magnesium and they perform single function (restriction) without methylation. Example are ECOR1 and HIND3
• Type III enzymes cleave at sites a short distance from a recognition site; require ATP or S-adenosyl-L-methionine and they do have methylation activity.
• Type IV enzymes are involved in DNA modification e.g. methylated, hydroxymethylated and glucosyl-hydroxymethylated DNA.