Publications by authors named "Kazumi Hata"

Outer surface protein A (OspA) is a crucial protein in the infection of Borrelia burgdorferi causing Lyme disease. We studied conformational fluctuations of OspA with high-pressure (15)N/(1)H two-dimensional NMR along with high-pressure fluorescence spectroscopy. We found evidence within folded, native OspA for rapid local fluctuations of the polypeptide backbone in the nonglobular single layer β-sheet connecting the N- and C-terminal domains with τ << ms, which may give the two domains certain independence in mobility and thermodynamic stability.

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To understand the pressure-adaptation mechanism of deep-sea enzymes, we studied the effects of pressure on the enzyme activity and structural stability of dihydrofolate reductase (DHFR) of the deep-sea bacterium Moritella profunda (mpDHFR) in comparison with those of Escherichia coli (ecDHFR). mpDHFR exhibited optimal enzyme activity at 50MPa whereas ecDHFR was monotonically inactivated by pressure, suggesting inherent pressure-adaptation mechanisms in mpDHFR. The secondary structure of apo-mpDHFR was stable up to 80°C, as revealed by circular dichroism spectra.

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The ionization of internal groups in proteins can trigger conformational change. Despite this being the structural basis of most biological energy transduction, these processes are poorly understood. Small angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR) spectroscopy experiments at ambient and high hydrostatic pressure were used to examine how the presence and ionization of Lys-66, buried in the hydrophobic core of a stabilized variant of staphylococcal nuclease, affect conformation and dynamics.

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