T7 DNA helicase: Difference between revisions
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'''T7 DNA helicase''' (gp4) is a hexameric motor protein encoded by [[T7 phage]]s that uses energy from [[Thymidine triphosphate|dTTP]] [[hydrolysis]] to process unidirectionally along single stranded [[DNA]], separating ([[helicase]]) the two strands as it progresses. It is also a [[primase]], making short stretches of RNA that initiates DNA synthesis.<ref name="ref 11">{{cite journal | vauthors = Lee SJ, Richardson CC | title = Choreography of bacteriophage T7 DNA replication | journal = Current Opinion in Chemical Biology | volume = 15 | issue = 5 | pages = 580–6 | date = October 2011 | pmid = 21907611 | doi = 10.1016/j.cbpa.2011.07.024 | pmc = 3195405 }}</ref> |
'''T7 DNA helicase''' (gp4) is a hexameric motor protein encoded by [[T7 phage]]s that uses energy from [[Thymidine triphosphate|dTTP]] [[hydrolysis]] to process unidirectionally along single stranded [[DNA]], separating ([[helicase]]) the two strands as it progresses. It is also a [[primase]], making short stretches of RNA that initiates DNA synthesis.<ref name="ref 11">{{cite journal | vauthors = Lee SJ, Richardson CC | title = Choreography of bacteriophage T7 DNA replication | journal = Current Opinion in Chemical Biology | volume = 15 | issue = 5 | pages = 580–6 | date = October 2011 | pmid = 21907611 | doi = 10.1016/j.cbpa.2011.07.024 | pmc = 3195405 }}</ref> Its homologs are found in mitochrondria (as [[TWINK]]) and chloroplasts.<ref name="pmid11431692">{{cite journal | vauthors = Spelbrink JN, Li FY, Tiranti V, Nikali K, Yuan QP, Tariq M, Wanrooij S, Garrido N, Comi G, Morandi L, Santoro L, Toscano A, Fabrizi GM, Somer H, Croxen R, Beeson D, Poulton J, Suomalainen A, Jacobs HT, Zeviani M, Larsson C | display-authors = 6 | title = Human mitochondrial DNA deletions associated with mutations in the gene encoding Twinkle, a phage T7 gene 4-like protein localized in mitochondria | journal = Nature Genetics | volume = 28 | issue = 3 | pages = 223–31 | date = July 2001 | pmid = 11431692 | pmc = | doi = 10.1038/90058 }}</ref><ref>{{cite journal |last1=Diray-Arce |first1=J |last2=Liu |first2=B |last3=Cupp |first3=JD |last4=Hunt |first4=T |last5=Nielsen |first5=BL |title=The Arabidopsis At1g30680 gene encodes a homologue to the phage T7 gp4 protein that has both DNA primase and DNA helicase activities. |journal=BMC plant biology |date=4 March 2013 |volume=13 |pages=36 |doi=10.1186/1471-2229-13-36 |pmid=23452619}}</ref> |
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==Crystal structure== |
==Crystal structure== |
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Revision as of 22:04, 28 March 2019
 | It has been suggested that this article be merged into T7 DNA polymerase#gp4. (Discuss) Proposed since March 2019. |
T7 DNA helicase (gp4) is a hexameric motor protein encoded by T7 phages that uses energy from dTTP hydrolysis to process unidirectionally along single stranded DNA, separating (helicase) the two strands as it progresses. It is also a primase, making short stretches of RNA that initiates DNA synthesis.[1] Its homologs are found in mitochrondria (as TWINK) and chloroplasts.[2][3]
Crystal structure
The crystal structure was solved to 3.0 Å resolution in 2000,[4] as shown in the figure. In (A), notice that the separate subunits appear to be anchored through interactions between an alpha helix and an adjacent subunit. In (B), there are six sets of three loops. The red loop, known as loop II, contains three lysine residues and is thought to be involved in binding the ssDNA that is fed through the center of the enzyme.
Mechanism of sequential dTTP hydrolysis
Crampton et al. have proposed a mechanism for the ssDNA-dependent hydrolysis of dTTP by T7 DNA helicase as shown in the figure below.[5] In their model, protein loops located on each hexameric subunit, each of which contain three lysine residues, sequentially interact with the negatively charged phosphate backbone of ssDNA. This interaction presumably causes a conformational change in the actively bound subunit, providing for the efficient release of dTDP from its dTTP binding site. In the process of dTDP release, the ssDNA is transferred to the neighboring subunit, which undergoes a similar process. Previous studies have already suggested that ssDNA is able to bind to two hexameric subunits simultaneously.[6]
See also
References
- ^ Lee SJ, Richardson CC (October 2011). "Choreography of bacteriophage T7 DNA replication". Current Opinion in Chemical Biology. 15 (5): 580–6. doi:10.1016/j.cbpa.2011.07.024. PMC 3195405. PMID 21907611.
- ^ Spelbrink JN, Li FY, Tiranti V, Nikali K, Yuan QP, Tariq M, et al. (July 2001). "Human mitochondrial DNA deletions associated with mutations in the gene encoding Twinkle, a phage T7 gene 4-like protein localized in mitochondria". Nature Genetics. 28 (3): 223–31. doi:10.1038/90058. PMID 11431692.
- ^ Diray-Arce, J; Liu, B; Cupp, JD; Hunt, T; Nielsen, BL (4 March 2013). "The Arabidopsis At1g30680 gene encodes a homologue to the phage T7 gp4 protein that has both DNA primase and DNA helicase activities". BMC plant biology. 13: 36. doi:10.1186/1471-2229-13-36. PMID 23452619.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Singleton MR, Sawaya MR, Ellenberger T, Wigley DB (June 2000). "Crystal structure of T7 gene 4 ring helicase indicates a mechanism for sequential hydrolysis of nucleotides". Cell. 101 (6): 589–600. doi:10.1016/S0092-8674(00)80871-5. PMID 10892646.
- ^ Crampton DJ, Mukherjee S, Richardson CC (January 2006). "DNA-induced switch from independent to sequential dTTP hydrolysis in the bacteriophage T7 DNA helicase". Mol. Cell. 21 (2): 165–74. doi:10.1016/j.molcel.2005.11.027. PMID 16427007.
- ^ Yu X, Hingorani MM, Patel SS, Egelman EH (September 1996). "DNA is bound within the central hole to one or two of the six subunits of the T7 DNA helicase". Nat. Struct. Biol. 3 (9): 740–3. doi:10.1038/nsb0996-740. PMID 8784344.
External links
- T7+DNA+Primase-Helicase+Protein at the U.S. National Library of Medicine Medical Subject Headings (MeSH)