Document Detail


Kinetic analysis of the genome packaging reaction in bacteriophage lambda.
MedLine Citation:
PMID:  19788336     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Bacteriophage lambda is a double-stranded DNA virus that infects the Escherichia coli bacterium. lambda genomic DNA is replicated via rolling circle replication, resulting in multiple genomes linked head to tail at the cos site. To insert a single lambda genome into the viral capsid, the lambda terminase enzyme introduces symmetric nicks, 12 bp apart, at the cos site, and then promotes a strand separation reaction, releasing the tail end of the previous genome and leaving a binary complex consisting of lambda terminase bound to the head end of the adjacent genome. Next, the genome is translocated into the interior of the capsid particle, in a process that requires ATP hydrolysis by lambda terminase. Even though DNA packaging has been studied extensively, currently no bulk assays are available that have been optimized to report directly on DNA translocation. Rather, these assays are sensitive to assembly steps reflecting formation of the active, DNA packaging machine. In this work, we have modified the DNase protection assay commonly used to study DNA packaging in several bacteriophage systems, such that it reports directly on the kinetics of the DNA packaging reaction. We have analyzed our DNA packaging data according to an N-step sequential minimal kinetic model and have estimated an overall packaging rate of 119 +/- 8 bp/s, at 4 degrees C and 1 mM ATP. Furthermore, we have measured an apparent step size for the this reaction (m(obs)) of 410 +/- 150 bp. The magnitude of this value indicates that our assay is most likely sensitive to both mechanical steps associated with DNA insertion as well as occasional slow steps that are repeated every >410 bp. These slow steps may be reflective of the pausing events observed in recent single-molecule studies of DNA packaging in bacteriophage lambda [Fuller, D. N., et al. (2007) J. Mol. Biol. 373, 1113-1122]. Finally, we show that either ATP or ADP is required for terminase cutting at cos, to generate the active, DNA packaging complex.
Authors:
Qin Yang; Carlos E Catalano; Nasib Karl Maluf
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochemistry     Volume:  48     ISSN:  1520-4995     ISO Abbreviation:  Biochemistry     Publication Date:  2009 Nov 
Date Detail:
Created Date:  2009-11-10     Completed Date:  2009-11-16     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  10705-15     Citation Subset:  IM    
Affiliation:
Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Denver, C238-P15, 12700 East 19th Avenue, Aurora, Colorado 80045, USA.
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MeSH Terms
Descriptor/Qualifier:
Adenosine Diphosphate / metabolism
Adenosine Triphosphate / metabolism
Bacteriophage lambda / genetics*
DNA Packaging*
Genome, Viral*
Kinetics
Chemical
Reg. No./Substance:
56-65-5/Adenosine Triphosphate; 58-64-0/Adenosine Diphosphate

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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