Yuji Goto

We have previously shown [Goto, Y., Calciano, L. J., & Fink, A. L. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 573-577] that beta-lactamase, cytochrome c, and apomyoglobin are maximally unfolded at pH 2 under conditions of low ionic strength, but a further decrease in pH, by increasing the concentration of HCl, refolds the proteins to the A state with properties similar to those of a molten globule state. To understand the mechanism of acid-induced refolding of protein structure, we studied the eff

The addition of HCl, at low ionic strength, to the native state of apomyoglobin, beta-lactamase, and cytochrome c caused these proteins to adopt an essentially fully unfolded conformation in the vicinity of pH 2. However, contrary to expectation, the addition of further acid resulted in refolding to a compact conformation with the properties of a molten globule. The major factor responsible for the refolding is believed to be the binding of the anion, which minimizes the intramolecular charge re

We present evidence that beta-lactamase is close to fully unfolded (i.e., random coil conformation) at low ionic strength at the extremes of pH and that the presence of salt causes a cooperative transition to a conformation with the properties of a molten globule, namely, a compact state with native-like secondary structure but disordered side chains (tertiary structure). The conformation of beta-lactamase I from Bacillus cereus was examined over the pH 1.5-12.5 region by circular dichroism (CD)

Alcohols denature the native state of proteins, and also stabilize the alpha-helical conformation in unfolded proteins and peptides. Among various alcohols, trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP) are often used because of their high potential to induce such effects. However, the reason why TFE and HFIP are more effective than other alcohols is unknown. Using CD, we studied the effects of TFE and HFIP as well as reference alcohols, i.e., methanol, ethanol, and isopropanol, on the

Nickel acetylacetonate was thermally decomposed in oleylamine under inert atmosphere. Nanocrystals of two cubic phases and a hexagonal phase appeared. The phases were identified using X-ray diffraction, laboratory X-ray photoelectron spectroscopy (XPS), and hard-X-ray photoelectron spectroscopy (HX-PES). The hexagonal phase was a nickel carbide, Ni3C, which had been often identified as a hexagonal close-packed metallic nickel. One cubic phase was a face-centered metallic nickel, and the other cu

Using heteronuclear NMR spectroscopy, we studied the solution structure and dynamics of bovine beta-lactoglobulin A at pH 2.0 and 45 degrees C, where the protein exists as a monomeric native state. The monomeric NMR structure, comprising an eight-stranded continuous antiparallel beta-barrel and one major alpha-helix, is similar to the X-ray dimeric structure obtained at pH 6.2, including betaI-strand that forms the dimer interface and loop EF that serves as a lid of the interior hydrophobic hole

Although metal ions such as Cu(2+), Zn(2+), and Fe(3+) are implicated to play a key role in Alzheimer disease, their role is rather complex, and comprehensive understanding is not yet obtained. We show that Cu(2+) and Zn(2+) but not Fe(3+) renders the amyloid beta peptide, Abeta(1-40), nonfibrillogenic in nature. However, preformed fibrils of Abeta(1-40) were stable when treated with these metal ions. Consequently, fibril growth of Abeta(1-40) could be switched on/off by switching the molecule b

Although bovine beta-lactoglobulin assumes a monomeric native structure at pH 3 in the absence of salt, the addition of salts stabilizes the dimer. Thermodynamics of the monomer-dimer equilibrium dependent on the salt concentration were studied by sedimentation equilibrium. The addition of NaCl, KCl, or guanidine hydrochloride below 1 M stabilized the dimer in a similar manner. On the other hand, NaClO(4) was more effective than other salts by about 20-fold, suggesting that anion binding is resp

Because of the insolubility and polymeric properties of amyloid fibrils, techniques used conventionally to analyze protein structure and dynamics have often been hampered. Ultrasonication can induce the monomeric solution of amyloidogenic proteins to form amyloid fibrils. However, ultrasonication can break down preformed fibrils into shorter fibrils. Here, combining these 2 opposing effects on beta(2)-microglobulin (beta2-m), a protein responsible for dialysis-related amyloidosis, we present tha