A UT Austin researcher is one of a team of scientists contributing to a study that has revealed a curious tube-shaped structure that a certain type of virus temporarily forms in order to deliver its DNA during the infection phase, consequently dissolving it after infection is complete. Dr. Ian Molineux, a professor of molecular genetics and microbiology at the University of Texas at Austin, joined eight other researchers in the study, which discovered that this unique mechanism found in the phiX174 bacteriophage virus, which attacks E. coli bacteria.
Unlike other viruses, this virus does not contain an obvious tail section for the transfer of its DNA into host cells. Instead, the “tube” structure grows only when it is needed to transfer DNA. It is a unique feature to this virus that has not been observed before. “This structure was completely unexpected,” said Bentley A. Fane, a professor in the BIO5 Institute at the University of Arizona. “No one had seen it before because it quickly emerges and then disappears afterward, so it’s very ephemeral.”
The only other phage virus known to operate even similarly to phiX174 is the T7 virus, which features a notably short tail that elongates when it is time to infect the host, according to Purdue postdoctoral research associate Lei Sun, who served as lead author of a research paper that appeared in the journal Nature on December 15th.
The tube-growing operation appears to be the work of a newly discovered H-protein structure. The capsid of the virus is composed of four proteins in total — H, J, F and G. Since the structures of all but the H protein had been previously determined, the H protein structure, which consists of 10 “alpha-helical” molecules coiled around each other, is believed to formulate the tube-shaped structure. And for good reason: phiX174 penetrates E. coli cells’ double membrane via the two ends of the virus’s H-protein tube, which attach to the host cell’s inner and outer membranes. “Like many other viruses, the shape of the phiX174 capsid has icosahedral symmetry, a roughly spherical shape containing 20 triangular faces.”
“This may be a general property found in viral-DNA conduits and could be critical for efficient genome translocation into the host,” Rossmann said.