sAβPPα is a Potent Endogenous Inhibitor of BACE1.

Proteolytic cleavage of the amyloid-β protein precursor (AβPP) by the enzyme BACE1 (BACE) is the initial step in production of amyloid-β peptide (Aβ), and as such has been a major target of Alzheimer's disease (AD) drug discovery efforts. Overproduction of Aβ results in neuronal cell death and accumulation of amyloid plaques in AD and in traumatic brain injury, and is also associated with stroke due to cerebral amyloid angiopathy. Herein we report for the first time that sAβPPα, the product of the cleavage of AβPP by α-secretase, is a potent endogenous direct inhibitor of the BACE enzyme, and that its inhibition is likely by an allosteric mechanism.

A green fluorescent protein solubility screen in E. coli reveals domain boundaries of the GTP-binding domain in the P element transposase.

Guanosine triphosphate (GTP) binding and hydrolysis events often act as molecular switches in proteins, modulating conformational changes between active and inactive states in many signaling molecules and transport systems. The P element transposase of Drosophila melanogaster requires GTP binding to proceed along its reaction pathway, following initial site-specific DNA binding. GTP binding is unique to P elements and may represent a novel form of transpositional regulation, allowing the bound transposase to find a second site, looping the transposon DNA for strand cleavage and excision.

THAP proteins target specific DNA sites through bipartite recognition of adjacent major and minor grooves.

THAP-family C(2)CH zinc-coordinating DNA-binding proteins function in diverse eukaryotic cellular processes, such as transposition, transcriptional repression, stem-cell pluripotency, angiogenesis and neurological function. To determine the molecular basis for sequence-specific DNA recognition by THAP proteins, we solved the crystal structure of the Drosophila melanogaster P element transposase THAP domain (DmTHAP) in complex with a natural 10-base-pair site. In contrast to C(2)H(2) zinc fingers, DmTHAP docks a conserved beta-sheet into the major groove and a basic C-terminal loop into the adjacent minor groove.

Native state energetics of the Src SH2 domain: evidence for a partially structured state in the denatured ensemble.

We have defined the free-energy profile of the Src SH2 domain using a variety of biophysical techniques. Equilibrium and kinetic experiments monitored by tryptophan fluorescence show that Src SH2 is quite stable and folds rapidly by a two-state mechanism, without populating any intermediates. Native state hydrogen-deuterium exchange confirms this two-state behavior; we detect no cooperative partially unfolded forms in equilibrium with the native conformation under any conditions.

Cross-resistance testing of next-generation nucleoside and nucleotide analogues against lamivudine-resistant HBV.

Several next-generation nucleoside and nucleotide analogues are currently in clinical development for the treatment of chronic hepatitis B. However, the efficacy of newer agents against lamivudine-resistant hepatitis B virus (HBV) has not been fully explored. To investigate this in vitro, we generated novel stable cell lines expressing HBV encoding the four major patterns of lamivudine resistance mutations (rtL180M+rtM204V, rtV173L+rtL180M+rtM204V, rtM204I and rtL180M+ rtM204I).