William S. Eng

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During neurotransmitter release at the synapse, influx of calcium ions stimulates the release of neurotransmitter. However, the mechanism by which synaptic vesicle fusion is coupled to calcium has been unclear, despite the identification of both the core fusion machinery [soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)] and the(More)
Membrane fusion between vesicles and target membranes involves the zippering of a four-helix bundle generated by constituent helices derived from target- and vesicle-soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). In neurons, the protein complexin clamps otherwise spontaneous fusion by SNARE proteins, allowing(More)
Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) catalyze compartment-specific membrane fusion. Whereas most SNAREs are bona fide type II membrane proteins, Ykt6 lacks a proteinaceous membrane anchor but contains a prenylation consensus motif (CAAX box) and exists in an inactive cytosolic and an active membrane-bound form. We(More)
Membrane fusion occurs when SNAREpins fold up between lipid bilayers. How much energy is generated during SNAREpin folding and how this energy is coupled to the fusion of apposing membranes is unknown. We have used a surface forces apparatus to determine the energetics and dynamics of SNAREpin formation and characterize the different intermediate structures(More)
A new functional class of SNAREs, designated inhibitory SNAREs (i-SNAREs), is described here. An i-SNARE inhibits fusion by substituting for or binding to a subunit of a fusogenic SNAREpin to form a nonfusogenic complex. Golgi-localized SNAREs were tested for i-SNARE activity by adding them as a fifth SNARE together with four other SNAREs that mediate Golgi(More)
The synthesis of the first iodinated juvenile hormone (JH) in enantiomerically enriched form is reported. This chiral compound, 12-iodo-JH I, has an iodine atom replacing a methyl group of the natural insect juvenile hormone, JH I, which is important in regulating morphogenesis and reproduction in the Lepidoptera. The unlabeled compound shows approximately(More)
Genetic and biochemical evidence has established that a SNARE complex consisting of syntaxin 5 (Sed5)-mYkt6 (Ykt6)-GOS28 (Gos1)-GS15 (Sft1) is required for transport of proteins across the Golgi stack in animals (yeast). We have utilized quantitative immunogold labeling to establish the cis-trans distribution of the v-SNARE GS15 and the t-SNARE subunits(More)
In regulated exocytosis, the core membrane fusion machinery proteins, the SNARE proteins, are assisted by a group of regulatory factors in order to couple membrane fusion to an increase of intracellular calcium ion (Ca(2+)) concentration. Complexin-I and synaptotagmin-I have been shown to be key elements for this tightly regulated process. Many studies(More)
Microvesicles (exosomes) are important mediators of intercellular communication, playing a role in immune regulation, cancer progression, and the spread of infectious agents. The biological functions of these small vesicles are dependent on their composition, which is regulated by mechanisms that are not well understood. Although numerous proteomic studies(More)
Cell surface glycans form a critical interface with the biological milieu, informing diverse processes from the inflammatory cascade to cellular migration. Assembly of discrete carbohydrate structures requires the coordinated activity of a repertoire of proteins, including glycosyltransferases and glycosidases. Little is known about the regulatory networks(More)