{"id":1265,"date":"2017-04-07T08:11:57","date_gmt":"2017-04-07T08:11:57","guid":{"rendered":"http:\/\/www.virologyhighlights.com\/?p=1265"},"modified":"2018-05-25T08:33:24","modified_gmt":"2018-05-25T08:33:24","slug":"genome-packaging-in-dsdna-viruses-is-regulated-by-a-pressure-sensitive-molecular-switch","status":"publish","type":"post","link":"https:\/\/www.elsevierblogs.com\/virology\/genome-packaging-in-dsdna-viruses-is-regulated-by-a-pressure-sensitive-molecular-switch\/","title":{"rendered":"Genome packaging in dsDNA viruses is regulated by a pressure-sensitive molecular switch"},"content":{"rendered":"

Read the full article on ScienceDirect.<\/a><\/h3>\n

Targeted mutagenesis of the P22 portal protein reveals the mechanism of signal transmission during DNA packaging<\/h2>\n

Text by Greg Bedwell
\n<\/em><\/p>\n

DNA packaging in dsDNA bacteriophage and herpesviruses relies on a powerful molecular motor to pump the viral genome into a pre-formed capsid.\u00a0 In these viruses, the gateway into the capsid is formed and regulated by a ring-like structure referred to as the viral portal.\u00a0 In its roles as both gateway and gatekeeper, the portal senses and responds to the density of DNA in the capsid interior and transmits that information to the motor on the capsid exterior.<\/p>\n

The work presented here began in 2014 as an effort to better understand the aspect of signal transmission during DNA packaging. We knew of two single point mutations in the portal of bacteriophage P22 that increased the amount of DNA packaged into virions.\u00a0 Mapping the location of these mutants onto the portal structure led us to realize that they were buried nearby the protein core.\u00a0 Unable to interact with DNA directly, how were these mutations working to effectively \u201cdesensitize\u201d the portal sensor?<\/p>\n

We knew that the answer to this question lay in better understanding the sensing mechanism itself.\u00a0 Using the already-identified overpackaging mutants as a springboard, we made additional mutants at these and other nearby residues to try to gain insight into how the sensing mechanism worked.\u00a0 To our surprise, all of our amino acid substitutions resulted in fully viable phage and unique overpackaging phenotypes.\u00a0 The trends that we observed led to the hypothesis that the overpackaging mutants were subtly altering the structure and\/or dynamics of the protein in this region. \u00a0We confirmed this hypothesis with various biophysical measurements made on purified proteins.<\/p>\n

We knew from structural data that the portal exists in two distinct pre- and post-packaging forms.\u00a0 Comparison of these two structures in the context of our data suggested that the dynamic perturbations we observed in our mutants made the \u201cnatural\u201d transition between forms more difficult to trigger due to changes in things like side chain packing.\u00a0 This was the clue that we needed to better define the sensing mechanism itself.\u00a0 DNA packaging is a continuous process that is accompanied by a continuous increase in pressure.\u00a0 The P22 portal undergoes significant compression during the process of packaging.\u00a0 Alterations in side chain packing are one of the key determinants in protein compressibility.\u00a0 Our findings indicate that viral portal proteins are biological pressure transducers.\u00a0 Pressure buildup inside the capsid during packaging induces gradual conformational changes in portal that eventually lead to packaging termination.<\/p>\n

\"blogpicturetailmachine\"<\/p>\n

Figure legend<\/h3>\n

During DNA packaging in P22, the dsDNA genome is pumped through the portal, a component of the tail machinery shown in the micrograph above.\u00a0 The findings of our study indicate that the portal serves as a macromolecular pressure sensor that responds to the continuous increase in pressure that accompanies DNA incorporation into the viral capsid.<\/p>\n

Introducing the authors<\/strong><\/h3>\n

\"58779<\/p>\n

Pictured:\u00a0Greg Bedwell (left), Research Fellow, Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute. Boston MA. (current) and\u00a0 Peter Prevelige, Professor, Department of Microbiology, University of Alabama at Birmingham, Birmingham AL.<\/p>\n

About the research<\/h3>\n

Targeted mutagenesis of the P22 portal protein reveals the mechanism of signal transmission during DNA packaging<\/a><\/strong>
\nGregory J. Bedwell, Peter E. Prevelige Jr.
\nVirology<\/em>, Volume 505, May 2017, Pages 127\u2013138<\/p>\n

 <\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Read the full article on ScienceDirect. Targeted mutagenesis of the P22 portal protein reveals the mechanism of signal transmission during DNA packaging Text by Greg Bedwell DNA packaging in dsDNA bacteriophage and herpesviruses relies on a powerful molecular motor to pump the viral genome into a pre-formed capsid.\u00a0 In these viruses, the gateway into the Read More…<\/a><\/p>\n","protected":false},"author":1,"featured_media":1266,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,629,633],"tags":[1047,1054,1055,1048,1051,1052,1049,1050,1053,1056],"class_list":["post-1265","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-highlighted-article","category-virus-replication","category-virus-structure","tag-bacteriophage","tag-dana-farber-cancer-institute","tag-dept-of-microbiology","tag-dna-packaging","tag-dsdna","tag-gregory-j-bedwell","tag-herpesviruses","tag-p22","tag-peter-e-prevelige-jr","tag-university-of-alabama"],"_links":{"self":[{"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/posts\/1265","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/comments?post=1265"}],"version-history":[{"count":5,"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/posts\/1265\/revisions"}],"predecessor-version":[{"id":1272,"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/posts\/1265\/revisions\/1272"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/media\/1266"}],"wp:attachment":[{"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/media?parent=1265"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/categories?post=1265"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.elsevierblogs.com\/virology\/wp-json\/wp\/v2\/tags?post=1265"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}