Area TE of the monkey inferior temporal cortex represents the final stage of the visual pathway responsible for object vision. Neurons in area TE respond selectively to particular object features which are more complex than simple bars and spots, but simpler than an ordinary real-world object. This area consists of columns of 0.4-0.5mm width, each containing cells responding to similar object features. The overall composition of an object may be represented by the combination of active columns.
Denaturation behaviors of sodium channels of squid axon ware studied, using aliphatic alcohols as denaturants. An irreversible suppression of sodium current that could be measured by the intraacellular perfusion was attributable to the denaturation of sodium channels. The denaturation time constant decreased as the alcohol concentration increased. The time constant was prop-ortional to the power of the alcohol concentration with the exponent between 4 and 8. The concentration of alcohol in membrane which denatured half of the sodium channels in 2 hours was about 0.5M irrespective of carbon number of alcohols. The mechanism of the stability of membrane proteins was discussed besed upon these experimental results together with the theoretical calulation of amino acid sequence of bacteriorhodopsin. It was suggested that the folding mechanism of membrane proteins is simpler than soluble proteins and the possibility to predict the molecular structure of membrane proteins was discssed.
Spherical multilamellar vesicles of dimyristoylphosphatidylglycerol (DMPG) prepared in the presence of NaCl up to 1M at a temperature of liquid crystalline phase was found to exist in a metastable state at a gel phase temperature. On annealing at 5°C of the gel temperature, the metastable self-assemblies of DMPG converted finally into a stable state of crystalline cylindrical vesicular structure wrapped by 8-10 bilayer lamellae. The conversion process was discussed, focusing on the area occupied by negatively charged head group of DMPG molecules related to their packing modes.
Phagocytic cytochrome b558 is a membrane-bound heme-containing enzyme that catalyzes one-electron reduction of O2 to produce superoxide anion. This cytochrome b has a low-spin 6-coordinate heme iron, and its catalytic activity is not inhibited by respiratory inhibitors such as CO. In this paper, the recent progress is reviewed focusing on the structure and the function of the cytochrome. Our spectroscopic and kinetic data suggest that cytochrome b558 catalyzes the O2- production without ligation of O2 to the heme iron during the catalytic cycle. The mechanisms of oxygen reduction and regulation of the electron transfer reactions are discussed.
Endoproteolytic processing of precursor proteins typically at specific pairs of basic amino acids is a key step in the production of bioactive peptides and proteins. The endrproteases involved in this process belong to a new family of Ca2+ -dependent serine proteases related to the yeast Kex2 protease. These include furin, PC2, PC3, PC4, PACE4 and PC6, all of which have been characterized structurally and functionally.