Summary: R.Pab1 restriction endonuclease
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R.Pab1 restriction endonuclease Provide feedback
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Miyazono KI, Watanabe M, Kosinski J, Ishikawa K, Kamo M, Sawasaki T, Nagata K, Bujnicki JM, Endo Y, Tanokura M, Kobayashi I; , Nucleic Acids Res. 2007; [Epub ahead of print]: Novel protein fold discovered in the PabI family of restriction enzymes. PUBMED:17332011 EPMC:17332011
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This tab holds annotation information from the InterPro database.
InterPro entry IPR018576
There are four classes of restriction endonucleases: types I, II,III and IV. All types of enzymes recognise specific short DNA sequences and carry out the endonucleolytic cleavage of DNA to give specific double-stranded fragments with terminal 5'-phosphates. They differ in their recognition sequence, subunit composition, cleavage position, and cofactor requirements [PUBMED:15121719, PUBMED:12665693], as summarised below:
- Type I enzymes (EC) cleave at sites remote from recognition site; require both ATP and S-adenosyl-L-methionine to function; multifunctional protein with both restriction and methylase (EC) activities.
- Type II enzymes (EC) cleave within or at short specific distances from recognition site; most require magnesium; single function (restriction) enzymes independent of methylase.
- Type III enzymes (EC) cleave at sites a short distance from recognition site; require ATP (but doesn't hydrolyse it); S-adenosyl-L-methionine stimulates reaction but is not required; exists as part of a complex with a modification methylase methylase (EC).
- Type IV enzymes target methylated DNA.
Type II restriction endonucleases (EC) 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 beta-strands and one alpha-helix, as well as a similar mechanism of cleavage, suggesting a common ancestral origin [PUBMED:15770420]. However, there is still considerable diversity amongst restriction endonucleases [PUBMED:14576294, PUBMED:11827971]. 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 [PUBMED:11557805].
This entry includes R.Pab1 from Pyrococcus abyssi. R.Pab1 is homodimeric and has a curved anti-parallel beta-sheet, which forms a three dimensional shape resembling a 'half pipe'. DNA-binding analyses identifies it as the double-strand DNA-binding site. It is able to catalyse the cleavage of 5'-GTAC generating a TA3' overhang in the absence of Mg2+ [PUBMED:17332011].
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Curation and family details
|Seed source:||Bateman A|
|Number in seed:||5|
|Number in full:||56|
|Average length of the domain:||116.20 aa|
|Average identity of full alignment:||69 %|
|Average coverage of the sequence by the domain:||53.14 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||5|
|Download:||download the raw HMM for this family|
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the RE_R_Pab1 domain has been found. There are 6 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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