February 2014-Present: Effects of mutants in the I-domain on Bacteriophage P22 coat protein stability and mature capsid structure
By Fejiro Okifo, Kevin Robbins, Dr. Carol Teschke
Department of Molecular and Cell Biology, University of Connecticut, Storrs
As common as the rhinovirus that visits itself upon us every flu season and as insidious as the HIV virus that causes AIDS, viruses have been afflicting the human race since the dawn of time. And yet there is still much to discover about the mechanism by which they infect their hosts. The purpose of this project is to understand the structural and dynamic components of viral infection. Structural information concerning protein interactions that occur during capsid assembly from the earliest and transient stages through maturation is not completely understood. Substantial subunit rearrangements have been observed in the formation of mature viral particles. I intend to use bacteriophage P22, a double-stranded DNA virus, as a model system in order to study virus assembly. P22 is ideal because a large number of dsDNA viruses including the Herpesviridiae use a common protein fold known as the HK97 fold as their major capsid protein. This HK97 fold contains extra domains in some viruses. In P22, the HK97 fold is termed the coat protein (CP) and contains a domain called the insertion domain, or I-domain, that is essential for coat protein folding and assembly into the mature virion. When this I-domain coat protein is absent, folding and consequently assembly is inhibited. I hypothesize that the I-domain serves as the folding nucleus of the coat protein. Known substitutions within the I-domain of the full-length coat protein lead to the formation of petite or incomplete mature capsids. This experiment will investigate how the substitutions affect I-domain structure and stability using techniques such as circular dichroism and NMR (Nuclear Magnetic Resonance) to gain atomic scale detail on the intra- and intermolecular interactions within the I-domain and within domains of full-length coat protein. The atomic-scale structural information gained from the NMR studies on the I-domain will identify important interactions required for stability and structural identity of the I-domain. These interactions will then be studied in order to better understand protein stability and protein assembly. Understanding how these capsids are assembled will assist in the development of antiviral drugs. P22 capsids are also proving useful in the field of nanotechnology and drug delivery platform. With viruses mutating millions of times faster than our own genome, it is especially crucial to investigate novel ways to dismantle virus assembly in order to fight virus-related diseases that plague myriads of people. Thus, the medical implications of this research are vast.