Hiroyuki Takashima

A new α-helical motif in membrane active peptides

A comparative analysis of the primary and secondary structures of the neurotoxins mast cell degranulating peptide apamin and charybdotoxin, and of the hormone endothelin revealed a strikingly homologous structural element consisting of an ?-helical stretch spanning the sequence portion Cys X-X-X Cys and stabilized by disulfide bridging to a second consensus sequence Cys X Cys, itself folded in a ?-type structure. This structural motif generates a certain degree of amphiphilicity for the folded molecules which may be correlated with the bioactivities of the neurotoxins at the membrane level. The presence of the identical structural motif in endothelin raises the question of whether it may represent, even for this hormone, the clue for its biological activity.

High-Resolution Protein Structure Determination by NMR

The quality of the three-dimensional structure of proteins determined by nmr is influenced by many factors. The factors are reviewed by focusing on structure calculation problems. High-performance computing implementations are introduced to improve the conformational sampling of the calculations. The quality and improvements of the nmr-derived structural information are also discussed.

Solution Structure of Neocarzinostatin Determined by Homonuclear Two-Dimensional Nuclear Magnetic Resonance

The secondary and tertiary structures of apo- and holoneocarzinostatin have been investigated by x-ray crystallography and spectroscopic methods. This chapter reviews the determination process of the three-dimensional structure of neocarzinostatin by the combined use of homonuclear two-dimensional nuclear magnetic resonance (NMR) and distance geometry calculations, which has been dramatically improved in the past decade. The protein moiety consists mainly of antiparallel β-sheets forming a β-barrel structure and a backbone sheet. The chromophore molecule is tightly enwrapped by the barrel and thus shielded from exposure to the solvent. The proteinchromophore interaction mechanism is also discussed in the context of release of the active chromophore and the activation mechanism of holo-neocarzinostatin.