The gustatory and olfactory cells can detect multifarious substances in external environments. Recently, bitter substances and odorants are suggested to be detected by direct adsorption on a lipid bilayer matrix without a specific receptor protein in receptor membranes and to cause a membrane potential and an impulse generation. In this review, we describe that the adsorption of various bitter and odor substances on a lipid bilayer matrix can be easily detected by observing a frequency change of a synthetic multibilayer-coated piezoelectric crystal in an aqueous or a gas phase. The adsorption process was followed by changes of a membrane potential and a membrane resistance of a synthetic bilayer membrane. The bilayer-coated crystal will become a new tool as an odor sensor and to study the biological mechanism of gustatory and olfactory cells.
The targeting of proteins to diffrent locations whithin the cell is often mediated by amino-terminal extentions called signal peptide. The interactions of two different classes of signal peptide (corresponding to two different mechanisms of protein processing) with phospholipid bilayer membrane were investigated by high sensitivity differential scanning calorimetry and steady-state fluorescence spectroscopy.
Mini-F plasmid has three genes sopA, sopB and sopC essential for partitioning the plasmid. The sopA and sopB genes code for 43.7Kd and 35.4Kd proteins, respectively. The cis-acting sopC region has twelve 43-bp direct repeats. Purified SopB protein binds to the sopC DNA. SopA protein acts as the repressor of the sopA-sopB operon in the presence of SopB protein. When plasmid-free segregants appear in cell division, they are killed postsegregationally by the ccd mechanism controlled by the ccdA and ccdB gene products of the plasmed.
Xenopus oocytes were injected with exogenous mRNA prepared from rat small intestine and kidney and their electrical responses to glucose and amino acids were measured electrophysiologically. Na+/glucose, amino acid cotransporters were expressed in the oocytes by injection of small intestine mRNA, while facilitated diffusion carrier protein(s) (uniporter) were mainly expressed by injection of kindney mRNA.
A growth factor and two growth inhibitors for adult rat hepatocytes were purified from rat platelets. Hepatocyte growth factor (HGF) seemed to be a hepatotropic factor which has not been purified during the past 30 years. One of growth inhibitors was identical to TGF-β. The other, named PDGI-α, was a new growth inhibitor. TGF-β masking protein that may be a regulator of the activity of TGF-β was also isolated from rat and human platelets.
The model of the acute differential sensitivity in taste of insect is introduced here. Modeling study shows that this can be realized through the central mechanism which CNS taste neuron integrates inputs from peripheral receptors. Such the mechanism is expected to contribute to the enhancement of the peripheral sensitivity in biological sensory system.
This article reviews the findings of recent systematic studies which examine the formation of a secondary structure of protein fragments and their analogue peptides in water solutions through the use of 2D-NMR spectroscopy. Some peptides form a transient secondary structure, and this structure (an elementary twist) then develops into a β-turn or an α-helix, depending upon changes in the environment of the peptide as well as the sequence context. The same formation must also take place in the first step of the folding process of a globular protein, since the formation of an elementary twist is fairly local, depending only on the interaction of a few neighboring residues.
This paper describes the analysis of amino acid sequence as well as the denaturation experiment of soluble globular and membrane proteins. The two kinds of proteins were discriminated by amino acid sequence almost completely, using only the hydrophobicity. The denaturation measurements lead to the conclusion that the hydrophobic interaction determines the form of proteins (i.e. globular or membrane proteins), while the polar interactions play major role in the tertiary structure formation.