Mechanisms of the Biological Activities of 
Membrane Glycoproteins 
Don C. Wiley, Ph.D. — Investigator 
Dr. Wiley is also Professor of Biochemistry and Biophysics at Harvard College and Research Associate in 
Medicine at the Laboratory of Molecular Medicine at the Children 's Hospital, Boston. He received his Ph.D. 
degree in biophysics from Harvard University. He then joined the faculty at Harvard and served as Assis- 
tant and Associate Professor of Biochemistry and Molecular Biology and as Associate Professor of Bio- 
chemistry and Biophysics before attaining his present position. Dr. Wiley is Chairman of the Committee 
on Higher Degrees in Biophysics. He is a Fellow of the American Academy of Arts and Sciences and a re- 
cipient of the Louisa Gross Horwitz Prize from Columbia University. Dr. Wiley was recently elected to the 
National Academy of Sciences. 
Tcell recognition occurs when cell surface his- 
tocompatibility glycoproteins present anti- 
gens, processed to small peptides, to an antibody- 
like molecule on the T cell receptor. Each 
organism has only a small number of different 
histocompatibility molecules (probably less than 
a dozen), so that each membrane glycoprotein 
must be able to "present" many, possibly thou- 
sands, of different antigenic peptides to thou- 
sands or more distinct T cell receptors through- 
out the immunological life of the individual. 
In the past few years our laboratory has deter- 
mined the three-dimensional structure of two hu- 
man-class histocompatibility antigens (HIA) by 
high -resolution x-ray crystallography. This re- 
sulted in the visualization of antigen presenta- 
tion, when an obvious peptide-binding cleft was 
revealed and shown to be filled with a presumed 
mixture of peptide antigens. Comparison of the 
structures of two polymorphic alleles of the hu- 
man histocompatibility antigen refined to 2.6 A 
resolution also suggested that the basis for allelic 
specificity, or "restriction," is in a set of pockets 
in the peptide-binding cleft. 
We recently crystallized one of the histocom- 
patibility antigens complexed with a peptide 
from influenza virus. This required reconstitut- 
ing HIA from its two polypeptide subunits in the 
presence of a "restricted" peptide. It appears 
that the HIA molecule required peptide to be re- 
constituted efficiently in vitro, arguing that pep- 
tide binding may be linked to subunit assembly or 
stability. 
In the past year, in collaboration with Jack Stro- 
minger and Joan Gorga, we crystallized a number 
of class II histocompatibility antigens and the 
complexes formed with superantigens. 
Our laboratory is also studying how influenza 
virus infects cells. About 10 years ago we deter- 
mined the three-dimensional structure of the in- 
fluenza virus hemagglutinin (HA), the viral gly- 
coprotein responsible for binding the virus to 
cells and for fusing the viral membrane to a cellu- 
lar membrane to effect infectious entry. Recently 
we determined the structure of a series of com- 
plexes between the HA and derivatives of sialic 
acid, the cellular receptor for influenza virus. 
Our laboratory has synthesized a number of 
these new ligands to confirm an atomic model 
for virus-cell binding that we proposed two 
years ago. 
This year, in collaboration with Jeremy 
Knowles, Gary Glick, and George Whitesides, we 
have analyzed the binding of virus to multiden- 
tate ligands and have discovered some dimeric 
and polymeric ligands with increased affinity. In 
the process a second binding site has been lo- 
cated on the HA at an interface between domains 
of the molecule, which although probably not 
physiological, may offer opportunities for the de- 
sign of a ligand to stabilize the interface against 
the conformational change required for the HA's 
membrane fusion activity. 
A number of other crystal lographic and bio- 
chemical studies are under way on influenza C 
virus, on a low-pH fusion-active conformation of 
the influenza HA, on trypanosome surface anti- 
gens, and on the glycoprotein of HIV-1 in com- 
plex with its receptor, CD4. 
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