William J. Lennarz
Ph.D. University of Illinois
Leading Professor and Chairman, Department of Biochemistry and Cell Biology
Director, Institute for Cell and Developmental Biology
Research Interests: Biosynthesis of glycoproteins; role of cell
surface glycoproteins in fertilization and early development.
Our laboratory is interested in understanding several steps involved in
glycoprotein synthesis, including N-glycosylation and protein folding, as
well as the functions of the glycan chains. We are using yeast, a simple
eukaryotic organism that can be genetically manipulated, to study glycoprotein
assembly. More specifically, we are investigating the enzymatic processes
of oligosaccharide addition and removal that occur in nascent polypeptides and
misfolded glycoproteins, respectively ( fig.1 ).
In addition, PDI, the enzyme that catalyzes folding and disulfide bond
formation in glycoproteins, is being studied ( fig.2 ).
With respect to the function(s) of oligosaccharide chains, glycoproteins have
also been shown to be involved in steps in fertilization in the sea urchin
and the frog ( fig.3 ). Egg receptors for sperm
have been characterized and cloned in both systems
( fig.4 ). Several lines of evidence suggest
that the oligosaccharide chains of a frog glycoprotein on the outer coat of
the egg are involved in the sperm binding process.
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Chi, Jung Hee, Roos, Jack, Dean, Neta (1996) The OST4 Gene of Saccharomyces
cerevisiae Encodes an Unusually Small Protein Required for Normal Levels
of Oligosaccharyltransferase Activity. J. Biol. Chem. 271, 3132-3140.
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Tian, Jingdong, Gong, Hui, Thomsen, Gerald H. and Lennarz, William J. (1997)
Gamete Interactions Xenopus laevis: Identification of Sperm Binding
Proteins in the Egg Vitelline Envelope. J. Cell Biol. 136, 1099-1108.
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Kitazume, Shinobu, Inoue, Sadako, Inoue, Yasuo and Lennarz, William J. (1997)
Identification of Sulfated Oligosialic Acid Units in the O-linked
Glycan of the Sea Urchin Egg Receptor for Sperm. Proc. Natl. Acad. Sci.
94, 3650-3655.
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Stears, Robin L. and Lennarz, William J. (1997) Re-examination of the Sequence
of the Sea Urchin Egg Receptor for Sperm: Implications with Respect to Its
Properties. Develop. Biol. 184, 25-30.
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Suzuki, Tadashi, Park, Hangil, Kitajima, Ken and Lennarz, William J. (1998)
Peptides Glycosylated in the Endoplasmic Reticulum of Yeast Are Subsequently
Deglycosylated by a Soluble Peptide: N-glycanase Activity. J. Biol.
Chem. 273, 21526-21530.
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