The conventional view of biosynthesis of membrane-embedded regions of integral membrane proteins is that the topology of membrane proteins is determined by signal-anchor sequences and signal-anchor sequence of type II. Here, we briefly review the evidence that in the case of integral membrane proteins with many membrane spans, and that the topology of membrane proteins is determined not only by signal-anchor sequences and signal-anchor sequence of type II, but also by signal-anchor sequence of type I. Evidence from band 3 study indicates that hydrophobic membrane peptide portions are not necessarily in contact with lipids in the membrane lipid bilayer and that even hydrophilic peptide portions are integrated into the lipid bilyar by the action of signal-anchor sequence of type I.
L-Glutamate is a major excitatory neurotransmitter in the mammalian central nervous system. It contributes not only to fast synaptic neurotransmission but also to complex physiological processes like plasticity, learning and memory. To terminate the action of glutamate and maintain its extracellular concentration below excitotoxic levels, glutamate is quickly removed by Na+-dependent glutamate transporters (EAATs). The glutamate/neutral amino acid transporter family consists of five EAATs (EAAT1-5) and two Na+-dependent neutral amino acid transporters (ASCT1-2). Here we focus on the structure and function of these transporters as well as on the indispensable pharmacological tool, such as a substrates and blockers, to clarify the physiological function of the transporter family.
All vertebrate cells, including muscle cells, contain nonmuscle myosin II which plays a role in a number of cell motility processes. Dynamic filament assembly-disassembly transition of myosin II molecules is particularly important in nonmuscle cells. In this review, we describe our recently proposed molecular mechanism for the filament formation of nonmuscle myosin II. We also discuss the distinct functions of two myosin II isoforms, IIA and IIB, during cell migration.
In alkaliphilic Bacillus, Na+-dependent pH homeostasis involves antiport activities as well as Na+ re-entry routes. MotPS that are homologous to MotAB are required for the Na+-dependent motility of alkaliphilic B. pseudofirmus OF4. Purified and reconstituted MotPS support amiloride analogue-sensitive Na+ flux. Mutants lacking functional MotPS display no deficit in pH homeostasis in pH shift experiments conducted with sub-optimal added [Na+] in the absence of solutes whose uptake is coupled to Na+ re-entry. By contrast, a role was evident for the recently described NaChBac (voltage-dependent) Na+ channel at sub-optimal [Na+]. NaChBac mutants exhibit a significant loss of pH homeostasis capacity.
Virtual neuron is a model neuron, which is expressed by a computer-executable format. Virtual neuron comprises all biochemical, biophysical, electrical and mechanical mechanisms lying behind the phenomena of a real neuron. Here, we show A-Cell software, which was developed for modeling and simulation of virtual neuron. A model for Ca/calmodulin-dependent protein kinase II (CaMKII) activation in a spine was constructed. The simulation of the A-Cell model showed the localized distribution of activated CaMKII near PSD (postsynaptic density). This localization could be a basis for the translocation of activated CaMKII to PSD, which was observed in experiments.