Ian J. Molineux
|Education:||Ph.D.: 1969, University of Oxford, England;|
|Postdoc.:||University of Wisconsin, Madison; Massachusetts Institute of Technology|
|Research:||Bacteriophage and host-parasite interactions|
The University of Texas at Austin
Molecular Genetics & Microbiology
1 University Station A5000
Austin TX 78712-0162
|Courses taught:||BIO 333 "Molecular Biology of Bacteriophages and Plasmids"
BIO 394 "Problems in Microbial Physiology: Nucleic Acids"
BIO 395J "Molecular Biology"
|Laboratory home page:|
The main interests of this laboratory are in understanding the interactions of bacteria and their parasites, both plasmids and bacteriophages. Two major lines of research are being followed, both use bacteriophage T7 or a related phage as a model parasite, with E. coli or other appropriate bacteria as hosts.
How hydrophilic nucleic acids pass through a hydrophobic lipid bilayer, as during phage or viral infection, or as eukaryotic RNA transport through the nuclear membrane is not understood. We are using infection by phage T7 as a model to study DNA translocation across the bacterial cell envelope. Proteins are ejected from the infecting virus particle, forming a channel across the periplasm and both the outer and inner membranes. Translocation of the genome is a slow process; it is initiated by a phage protein molecular motor comprised of two of the ejected virion proteins, which ratchet in the leading 850 bp at ~75 bp/sec at 30˚C. Mutations that alter one of these proteins allow the entire genome to enter the cell at a constant rate of 75 bp/sec and in the absence of any transcription. However, normally promoters on the leading 850 bp allow E. coli RNA polymerase to pull ~7 kb of the genome at 40 bp/sec by transcribing the early region. Finally, T7 RNA polymerase completes genome internalization at ~250 bp/sec. In the absence of newly synthesized T7 proteins, E. coli RNA polymerase internalizes the T7 genome at a faster rate than that of mRNA synthesis in vivo, being controlled by the same antitermination system that directs rRNA synthesis.
Current projects include the localization of the T7 proteins ejected from the infecting particle that are involved in translocating the phage genome into the bacterial cytoplasm and the mechanism of transcription antitermination that operates to make genome entry faster and more efficient. We can also stop translocation of the phage genome at a defined position during its entry into the cell, and are mapping the path of the DNA through the proteins that constitute the trans-membrane channel.
T7 is the prototype of a large family of phages that infect a variety of bacteria ranging from E. coli through Pseudomonas spp. and marine bacteria. Although there are notable differences, many of these phage genomes have preserved the same genetic organization as T7 and we are interested in why evolutionary forces have selected the overall constancy but also specific variations of the basic genome structure and how it may have occurred. Current evolutionary-related projects include assessing the effects of deleting essential or conditionally essential genes of the phage, of rearranging gene order, and of the origins of phage RNA polymerase-promoter specificities by evolving better growing variants. Mutations arising in response to selection are analyzed for their effects on phage fitness.
Grayson, P. and I. J. Molineux. Is phage DNA "injected" into cells - biologists and physicists can agree. Curr. Op. Microbiol. (2007) In press
Molineux, I. J. Fifty-three years since Hershey and Chase; much ado about pressure, but which pressure is it? Virology, 34 (2006): 221-229.
Molineux, I. J. No syringes please, ejection of T7 DNA from the virion is enzyme-driven. Mol. Microbiol. 40 (2001): 1-8.
Leiman, P. G., A. J. Battisti, V. D. Bowman, K. Stummeyer, M. Mühlenhoff, R. Gerardy-Schahn, D. Scholl, and I. J. Molineux.. Structure and evolution of viral organelles that digest extracellular polysaccharides of pathogenic bacteria. J. Mol. Biol. 371 (2007): 836-849.
Bull, J. J., R. Springman, and I. J. Molineux. Compensatory evolution in response to orthologous replacement of a central network gene. Mol. Biol. Evol. 24 (2007): 900-908.
Kemp, P., L. R. Garcia, and I. J. Molineux. Changes in bacteriophage T7 virion structure at the initiation of infection. Virology 340 (2005): 310-317.
Heineman, R. H., I. J. Molineux, and J. J. Bull. Evolutionary robustness of an optimal phenotype: re-evolution of lysis in a bacteriophage deleted for its lysin gene. J. Mol. Evol. 61 (2005): 181-191.
Kemp, P., M. Gupta, and I. J. Molineux. Bacteriophage T7 DNA ejection into cells is initiated by an enzyme-like mechanism. Mol. Microbiol. 53 (2004): 1251-1265.
Moak, M., and I. J. Molineux. Peptidoglycan hydrolytic activities associated with bacteriophage virions. Mol. Microbiol. 51 (2004): 1169-1183.
Cheng, X., W. Wang, and I. J. Molineux. F exclusion of bacteriophage T7 occurs at the cell membrane. Virology 326 (2004): 340-352.
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