World Library  
Flag as Inappropriate
Email this Article

T7 DNA Helicase

Article Id: WHEBN0004529808
Reproduction Date:

Title: T7 DNA Helicase  
Author: World Heritage Encyclopedia
Language: English
Subject: DNA replication, POLD4, Autonomously replicating sequence, HolD, SSBP2
Publisher: World Heritage Encyclopedia

T7 DNA Helicase

T7 DNA helicase is a hexameric motor protein that uses energy from dTTP hydrolysis to process unidirectionally along single stranded DNA, separating the two strands as it progresses.

Crystal structure

The crystal structure was solved to 3.0 Å resolution in 2000,[1] 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.[2] 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.[3]

See also


  1. ^ 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.  
  2. ^ 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.  
  3. ^ 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.  

External links

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.