Journal of Virology, June 2001, p. 5343-5351, Vol. 75, No. 11
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.11.5343-5351.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
2-Adaptin, a Clathrin Adaptor-Related Protein
Institute for Medical Microbiology and Hygiene, Johannes Gutenberg-Universität Mainz, D-55101 Mainz, Germany
Received 15 November 2000/Accepted 9 March 2001
For the outcome of a hepatitis B virus (HBV) infection, the viral L
envelope protein with its pre-S domain performs pivotal functions by
mediating attachment of HBV to liver cells, envelopment of viral
capsids, release of (sub)viral particles, regulation of supercoiled DNA
amplification, and transcriptional transactivation. To assess its
multiple functions and host-protein assistance involved, we initiated a
two-hybrid screen using the L-specific pre-S1 domain as bait. With this
approach, we have identified
2-adaptin, a putative member of the
clathrin adaptor proteins responsible for protein sorting and
trafficking, as a specific binding partner of L protein. Evidence for a
physical interaction between L protein and
2-adaptin was also
demonstrated by affinity chromatography and coimmunoprecipitation, and
the binding sites were mapped to the L-specific pre-S1 domain and the
2-adaptin-specific ear domain. The specificity of the interaction
was further sustained by the failure of
1-adaptin, a closely related
2-adaptin homologue, to associate with L protein. Analysis of an L
mutant protein indicates that the L-
2-adaptin interaction strictly
depends on the pre-S1 domain of transmembrane L protein oriented to the
cytosol and thus appears to occur in the cytosolic environment.
Interestingly, coexpression of the two interacting partners in
transfected cells resulted in recruitment of
2-adaptin by L protein
onto cis-Golgi-like structures, strongly indicating that
the association is physiologically relevant. Together, the results
suggest a role for
2-adaptin in L-mediated processes of viral
biogenesis and/or pathogenesis, such as facilitating and guiding HBV assembly.
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