LIS - Legume Information System
Information about legume traits for crop improvement
CicerMine
v5.1.0.3
Cicer data from the Legume Information System
v5.1.0.3
Cicer data from the Legume Information System
| Type | Homologous_superfamily |
| Description | Type II restriction endonucleases ( ) are components of prokaryotic DNA restriction-modification mechanisms that protect the organism against invading foreign DNA. These site-specific deoxyribonucleases catalyse the endonucleolytic cleavage of DNA to give specific double-stranded fragments with terminal 5'-phosphates. Of the 3000 restriction endonucleases that have been characterised, most are homodimeric or tetrameric enzymes that cleave target DNA at sequence-specific sites close to the recognition site. For homodimeric enzymes, the recognition site is usually a palindromic sequence 4-8 bp in length. Most enzymes require magnesium ions as a cofactor for catalysis. Although they can vary in their mode of recognition, many restriction endonucleases share a similar structural core comprising four β-strands and one α-helix, as well as a similar mechanism of cleavage, suggesting a common ancestral origin [ ]. However, there is still considerable diversity amongst restriction endonucleases [, ]. The target site recognition process triggers large conformational changes of the enzyme and the target DNA, leading to the activation of the catalytic centres. Like other DNA binding proteins, restriction enzymes are capable of non-specific DNA binding as well, which is the prerequisite for efficient target site location by facilitated diffusion. Non-specific binding usually does not involve interactions with the bases but only with the DNA backbone []. This superfamily represents the helical domain of AvaI and BsoBI restriction endonucleases, both of which recognise the double-stranded sequence CYCGRG (where Y = T/C, and R = A/G) and cleave after C-1 [ ]. Structurally, this domain consists of two long alpha helices joined by some shorter ones. One of the longer helices curves inwards towards DNA, while the other is kinked outwards. BsobI is made up of this helical domain, and another more compact globular domain (consisting of smaller helices and some beta strand elements). Within the endonuclease, this domain plays a role in DNA binding, so that the globular (catalytic domain) has a higher concentration of localised substrate []. |
| Short Name | Restr_endonucII_AvaI/BsoBI_hel |
