William J. Lennarz

Learn More
Protein disulfide isomerase plays a key role in catalyzing the folding of secretory proteins. It features two catalytically inactive thioredoxin domains inserted between two catalytically active thioredoxin domains and an acidic C-terminal tail. The crystal structure of yeast PDI reveals that the four thioredoxin domains are arranged in the shape of a(More)
It has been proposed that cytoplasmic peptide:N-glycanase (PNGase) may be involved in the proteasome-dependent quality control machinery used to degrade newly synthesized glycoproteins that do not correctly fold in the ER. However, a lack of information about the structure of the enzyme has limited our ability to obtain insight into its precise biological(More)
Asparagine-linked glycosylation is the most ubiquitous protein co-translational modification in the endoplasmic reticulum (ER). The enzyme that catalyzes this process is called oligosaccharyl transferase (OT). It catalyzes the transfer of an oligosaccharyl moiety (Glc3Man9GlcNAc2) from the dolichol-linked pyrophosphate donor to the side chain of Asn within(More)
During endoplasmic reticulum-associated degradation, the multifunctional AAA ATPase p97 is part of a protein degradation complex. p97 associates via its N-terminal domain with various cofactors to recruit ubiquitinated substrates. It also interacts with alternative substrate-processing cofactors, such as Ufd2, Ufd3, and peptide:N-glycanase (PNGase) in(More)
The enzymatic transfer of the oligosaccharide moiety from an oligosaccharide-lipid to denatured forms of three secretory proteins--ovalbumin, alpha-lactalbumin, and ribonuclease A--has been demonstrated utilizing a membrane fraction from hen oviduct. Based on a survey of 10 proteins denatured by sulfitolysis, the presence of the tripeptide sequence(More)
Deglycosylation of misfolded proteins by the endoplasmic reticulum-associated degradation (ERAD) pathway is catalyzed by peptide:N-glycanases (PNGases) that are highly conserved among mammals and yeast. The catalytic mechanism of PNGases employs a catalytic triad consisting of Cys, His and Asp residues, which is shared by other enzyme families such as(More)
In a microsome system rendered competent in protein translation by the addition of rabbit reticulocyte lysate, co-translational insertion and glycosylation of N-linked glycoproteins is observed when the appropriate mRNA is supplied. We have utilized this system to examine the ability of acceptor tripeptides of the type Asn-X-Thr/Ser to inhibit(More)
A quantitative assay was developed to study the interaction of Xenopus laevis sperm and eggs. Using this assay it was found that sperm bound in approximately equal numbers to the surface of both hemispheres of the unfertilized egg, but not to the surface of the fertilized egg. To understand the molecular basis of sperm binding to the egg vitelline envelope(More)