Bovine heart cytochrome c oxidase is an integral protein incorporated in the mitochondrial inner membrane, which reduces molecular oxygen to water, coupled with pumping protons from matrix side to entermembrane space. The crystal structures in fully oxidized and fully reduced states were determined at 2.30 and 2.35 Å resolutions, respectively. A tyrosine residue has a covalent bond with a histidine residue, a ligand of CuB. An aspartate residue apart from the O2 reduction site exchanges ets effective accessibility to the matrix aqueous phase for one to intermembrane space by a change of oxidation state. The movement indicates that the aspartate serves as a proton pumpong site.
Genes participating in excitation-contraction coupling in Caenorhabditis elegans are cloned and these mutant phenotypes are characterized. These are the ryanodime receptor gene unc-68, troponin C gene pat-10 and tropomyosin gene lev-11. Unc-68 mutant animal is viable and has weak phenotype even in the null mutation. Contrary to our expectation, mutant analysis on pat-10 and lev-11 suggests that functional defects of the proteins affect not only function of muscle contraction but also muscle development of the animal. Experimental strategy and procedures are also useful for those who have interest in handling the model animal.
Study of fast-folding small proteins has recently been making great peogress. Experimentally, the folding transition state has been characterized by using protein engineering approach. From the theoretical side, folding pathway can be successfully described by recently developed approaches of computer simulations and statistical mechanics. Combination of theoretical studies with experiments will lead us complete understanding of protein folding in near future.
Biological sequence analysis based on hidden Markov models (HMMs) is no doubt one of the most successful endeavors in the field of bioninformatics. HMMs are widely used not only for motif search but also for gene finding and protein fold recognition nowadays. Compared with existing models, HMMs possess flexibility to describe complex structures of sequence information. Moreover, various kinds of computer algorithms based on HMMs which enable us to model and interpret biological sequence data have been developed. In this paper, we introduce recent research topics of biological sequence analysis using HMMs and discuss a future perspective of the research.
Cells show a variety of responses to mechanical stimuli which deform the cell membrane. In other word, cells can sense their shape change. However, the molecular mechanism of mechanosensation of the cell had remained unknown for a long time. This situation has been changed since the discovery of a mechanosensitive ion channel called stretch activated (SA) channel. The most popular type of SA channels is a Ca2+ -permeable type with a single channel conductance of ca. 40pS. Though we know little about their physiological functions in nonsensory cells, activation of SA channels may increase intracellular Ca2+ concentration, thereby elicits proper cell responses. This short article focuses on the recent progress in the SA channel-mediated signaling mechanism in the stretch-induced cell remodelling, where spatiotemporal structures of mechanical stresses are converted into the structure of cell.
Olfactory signal transduction starts at the ciliary membrane of the receptor cells located in the olfactory epithelium. This transduction is triggerd by the G-protein-coupled seven transmembrane receptor, which in turn activates adenylyl cyclase-cAMP second messenger system. These chemical reactions finally lead to a sequential opening of cAMP-gated channel and Ca-activated Cl channel. Olfactory sensation is known to exhibit strong adaptation to the applied smell environment. This adaptation is regulate by a Ca-feedback to the cAMP-gated channel.