posted on 2020-07-28, 17:08authored byAngela Patterson, Zhongchao Zhao, Elizabeth Waymire, Adam Zlotnick, Brian Bothner
While there is an effective vaccine for Human Hepatitis B Virus
(HBV), 257 million people have chronic infections for which there
is no cure. The assembly process for the viral capsid is a potential
therapeutic target. In order to understand the capsid assembly process,
we investigated the dimeric building blocks of the capsid. To understand
what blocks assembly, we took advantage of an assembly incompetent
mutant dimer, Cp149-Y132A, located in the interdimer interface. This
mutation leads to changes in protein dynamics throughout the structure
of the dimer as measured by hydrogen–deuterium exchange mass
spectrometry (HDX-MS). To further understand how the HBV capsid assembles,
the homologue woodchuck HBV (WHV) capsid protein dimer (Cp) was used.
WHV is more stable than HBV in HDX-MS and native mass spectrometry
experiments. Because the WHV Cp assembles more rapidly into viral
capsids than HBV, it was suspected that an increase in stability of
the intradimer interface and/or in the contact region leads to increased
assembly rates. The differences in dynamics when comparing HBV and
human Cp149-Y132A as well as the differences in dynamics when comparing
the HBV and WHV Cps allowed us to map an allosteric network within
the HBV dimer. Through a careful comparison of structure, stability,
and dynamics using four different capsid protein dimers, we conclude
that protein subunit dynamics regulate HBV capsid assembly.