{{Short description|Enzyme}} {{Infobox nonhuman protein |Name=Type-2 restriction enzyme HaeIII |Symbol=haeIIIR |Organism = ''Haemophilus aegyptius'' | TaxID = 197575 |UniProt=O68584 |image= HaeIII-methyltransferase-dna-pdb-1DCT.png |caption= The crystal structure of HaeIII enzyme convalently complexed to DNA: an extrahelical cytosine and rearranged base pairing. | EntrezGene = | HomoloGene = | PDB = | RefSeqmRNA = | RefSeqProtein = WP_006996034.1 | ECnumber = 3.1.21.4 | Chromosome = Genomic | EntrezChromosome = NC_014920.1 | GenLoc_start = 698503 | GenLoc_end = 699745 }} {{Pfam box |Pfam=PF09556 |InterPro=IPR019059 |Name=HaeIIIR |Symbol=RE_HaeIII}} '''HaeIII''' is one of many restriction enzymes (endonucleases) a type of prokaryotic DNA that protects organisms from unknown, foreign DNA.<ref name=":0">{{Cite web|url=https://www.ebi.ac.uk/interpro/entry/InterPro/IPR019059/|title=InterPro|website=www.ebi.ac.uk|access-date=2020-04-06}}</ref> It is a restriction enzyme used in molecular biology laboratories. It was the third endonuclease to be isolated from the ''Haemophilus aegyptius'' bacteria. The enzyme's recognition site—the place where it cuts DNA molecules—is the GGCC nucleotide sequence which means it cleaves DNA at the site 5′-GG/CC-3. The recognition site is usually around 4-8 bps.<ref name=":0" /> This enzyme's gene has been sequenced and cloned. This is done to make DNA fragments in blunt ends. HaeIII is not effective for single stranded DNA cleavage.
==Properties== HaeIII has a molecular weight of 37126. After a 2-10-fold of HaeIII takes place, there is overdigestion of a DNA substrate. This results in 100% being cut, more than 50% of fragments being ligated, and more than 95% being recut. Heat inactivation comes at about 80 °C for 20 minutes. The locus of the ''Hae''III enzyme is on AF05137, and is linear with 957 base pairs.
==History== HaeIII along with other restriction enzymes were discovered in 1970 by Werner Arber and Matthew Meselson. The HaeIII methyltransferase also known as the MTase gene from ''Haemophilus aegyptius'' (recognition sequence: 5′-GGCC-3′) was made into ''Escherichia coli (E.coli)'' in the plasmid vector pBR322. The gene was extracted from a single ''Eco''RI fragment and a single ''Hind''III enzyme fragment. Clones carrying additional adjacent fragments were found to code for the ''Hae''III restriction enzyme.
==Function== The enzyme cleaves the DNA at the positions where the GGCC sequence is found. The cleavage occurs between the second and the third nucleotides (G and C). The resulting DNA fragments are known as restriction fragments. HaeIII cuts both strands of DNA in the same location, yielding restriction fragments with blunt ends. Heat denaturation occurs at 80°C after 20 minutes.<ref>{{cite web | url = http://www.thelabrat.com/restriction/HaeIII.shtml | title = HaeIII Restriction Enzyme | work = theLabRat.com | date = 2005 }}</ref>
==Methylase== ''Haemophilus aegyptius'' also carries a methylase dubbed '''HaeIIIM''' ({{uniprot|P20589}}) that methylates the internal cytosines in the GGCC sequence. It protects sequences from being cut by HaeIII, and forms a restriction modification system. HaeIII enzyme comes from an ''E. coli'' strain that carries the cloned HaeIII modification gene from ''Haemophilus aegyptius.''
==References== {{Reflist}}
== Further reading == {{refbegin}} * {{cite book | last = Rawn | first = J. David | name-list-style = vanc | date = 1989 | title = Biochemistry | publisher = Neil Patterson Publishers | edition = International | isbn = 0-89278-405-9 }} * {{cite journal | vauthors = Slatko BE, Croft R, Moran LS, Wilson GG | title = Cloning and analysis of the HaeIII and HaeII methyltransferase genes | journal = Gene | volume = 74 | issue = 1 | pages = 45–50 | date = December 1988 | pmid = 3248732 | doi = 10.1016/0378-1119(88)90248-x }} * {{cite journal | vauthors = Blakesley RW, Dodgson JB, Nes IF, Wells RD | title = Duplex regions in "single-stranded" phiX174 DNA are cleaved by a restriction endonuclease from Haemophilus aegyptius | journal = The Journal of Biological Chemistry | volume = 252 | issue = 20 | pages = 7300–6 | date = October 1977 | doi = 10.1016/S0021-9258(19)66969-3 | pmid = 71298 | doi-access = free }} * {{cite journal | vauthors = Hoffman JL | title = Chromatographic analysis of the chiral and covalent instability of S-adenosyl-L-methionine | journal = Biochemistry | volume = 25 | issue = 15 | pages = 4444–9 | date = July 1986 | pmid = 3530324 | doi = 10.1021/bi00363a041 }} {{refend}} {{restriction enzyme}} {{3.1-enzyme-stub}} Category:Restriction enzymes