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Regulation of Capsid Sizes of Large Tailed Bacteriophages

Hua, Jianfei (2010) Regulation of Capsid Sizes of Large Tailed Bacteriophages. Master's Thesis, University of Pittsburgh. (Unpublished)

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Many bacteriophages and eukaryotic viruses, which share little sequence similarities, have icosahedral protein capsids containing their genetic materials. Generally, an icosahedral viral capsid is assembly of 12 pentamers and a certain number of hexmers of the major capsid protein, following Caspar and Klug¡¯s quasi-equivalence rule. The arrangement of these pentamers and hexmers is characterized by the triangulation (T) number. Questions arise whether viruses have evolved from a few common ancestors, and how the assembly of the icosahedral capsids has been regulated to achieve a defined capsid size and geometry. I present studies of the capsids of several large icosahedral bacteriophages, which broaden our understanding of the regulation of viral capsid assembly. Bacteriophage SPO1 may share common ancestry with herpesvirus, according to the similarities in their T numbers and in the asymmetric molecules slightly off the local three-fold symmetry positions on the outer surface of both capsids. However, the cryo-EM structure of the SPO1 capsid assembled from the uncleaved major capsid protein show that, unlike the herpesvirus asymmetric molecule, the SPO1 asymmetric protein may not be required for the initial procapsid assembly, suggesting that the two asymmetric molecules may have different origins. Phage P1 is excellent for studying size determination in viral capsid since it produces virions of three sizes. The cryo-EM structures of the three capsids and internal capsid proteins identified suggests a control mechanism for P1 capsids, in which the DarA protein functions as a semi-scaffolding protein to assist the assembly of the P1 big capsid. Jumbo phages have been rarely studied. The structural studies on four jumbo phages showed their T numbers. N3, PAU and 121Q are the first T = 19, 25 and 28 viral capsids found. These results suggest that T-numbers larger than 16 may generally be allowed.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Hua, Jianfeijih27@pitt.eduJIH27
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairHendrix, Rogerrhx@pitt.eduRHX
Committee MemberConway, Jamesjxc100@pitt.eduJXC100
Committee Member Cascio, Michaelcascio@pitt.eduCASCIO
Committee MemberZhang, Peijunpez7@pitt.eduPEZ7
Date: 24 June 2010
Date Type: Completion
Defense Date: 20 November 2009
Approval Date: 24 June 2010
Submission Date: 8 December 2009
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Molecular Biophysics and Structural Biology
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: bacteriophages; capsid assembly; capsid size; capsid structure; croy-EM; decoration protein; icosahedral capsids; jumbo phages; major capsid protein; minor capsid protein; P1; SPO1; triagulation number; viral capsid evolution
Other ID:, etd-12082009-150454
Date Deposited: 10 Nov 2011 20:09
Last Modified: 15 Nov 2016 13:53


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