Functional characterization of the evolutionarily divergent fern plastocyanin

De functie van eiwitten die betrokken zijn bij insulinewerking en glucose hemeostrase en de rol van genetische varianten hierin bij de ontwikkeling van type 2 diabete

ゲンチョ ノウシツナイ シンケイモウ ノ キゲン トナル シンケイ サイボウ

The distribution and cell morphology of the cells which contribute to the supra-ependymal plexus in the rat were studied by retrograde labeling technique using cholera toxin subunit B(CTB), as a tracer. After injection of CTB into the lateral ventricle, highly labeled profiles were seen in the supra-ependymal plexus, while tanycytes of the third ventricle and a large number of cells in the dorsal raphe nucleus were also strongly labeled. Ependymocytes, subependymal glial cells and a few neurons in the subfornical organ and the hypothalamus (including the paraventricular hypothalamic nucleus) exhibited l[?]ow levels of labeling. Labeled cells of the dorsal raphe nucleus were most commonly located in the caudal half of the nucleus. They formed two cell groups; as a ventral group near the medial longitudinal fascicle and the dorsal one just beneath the aqueduct. Labeled cells in the dorsal group extended their dendrites to dorsomedially or dorolaterally, while the dendrites of labeled cells in the ventral group were oriented dorsally and ventrally. Dorsally, dorsomedially or dorsolaterally oriented dendrites from both groups run just beneath the aqueduct. The results or the present study show that almost all of the cells of origin of the supra-ependymal plexus extend their dendrites toward the ependyma. We assume that this peculiar dendritic organization allows the cells to monitor the ventriculor milieu

A QM/MM study of the nature of the entatic state in plastocyanin

Plastocyanin is a copper containing protein that is involved in the electron transfer process in photosynthetic organisms. The active site of plastocyanin is described as an entatic state whereby its structure represents a compromise between the structures favored by the oxidized and reduced forms. In this study, the nature of the entatic state is investigated through density functional theory-based hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations. The strain energy is computed to be 12.8 kcal/mol and 14.5 kcal/mol for the oxidized and reduced forms of the protein, indicating that the active site has an intermediate structure. It is shown that the energy gap between the oxidized and reduced forms varies significantly with the fluctuations in the structure of the active site at room temperature. An accurate determination of the reorganization energy requires averaging over conformation and a large region of the protein around the active site to be treated at the quantum mechanical level

Initial characteristics of RbcX proteins from Arabidopsis thaliana

Form I of Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) is composed of eight large (RbcL) and eight small (RbcS) subunits. Assembly of these subunits into a functional holoenzyme requires the assistance of additional assembly factors. One such factor is RbcX, which has been demonstrated to act as a chaperone in the assembly of most cyanobacterial Rubisco complexes expressed in heterologous system established in Escherichia coli cells. Analysis of Arabidopsis thaliana genomic sequence revealed the presence of two genes encoding putative homologues of cyanobacterial RbcX protein: AtRbcX1 (At4G04330) and AtRbcX2 (At5G19855). In general, both RbcX homologues seem to have the same function which is chaperone activity during Rubisco biogenesis. However, detailed analysis revealed slight differences between them. AtRbcX2 is localized in the stromal fraction of chloroplasts whereas AtRbcX1 was found in the insoluble fraction corresponding with thylakoid membranes. Search for putative “partners” using mass spectrometry analysis suggested that apart from binding to RbcL, AtRbcX1 may also interact with β subunit of chloroplast ATP synthase. Quantitative RT-PCR analysis of AtRbcX1 and AtRbcX2 expression under various stress conditions indicated that AtRbcX2 is transcribed at a relatively stable level, while the transcription level of AtRbcX1 varies significantly. In addition, we present the attempts to elucidate the secondary structure of AtRbcX proteins using CD spectroscopy. Presented results are the first known approach to elucidate the role of RbcX proteins in Rubisco assembly in higher plants

ATP synthase: evolution, energetics, and membrane interactions

The synthesis of ATP, life's 'universal energy currency', is the most prevalent chemical reaction in biological systems, and is responsible for fueling nearly all cellular processes, from nerve impulse propagation to DNA synthesis. ATP synthases, the family of enzymes that carry out this endless task, are nearly as ubiquitous as the energy-laden molecule they are responsible for making. The F-type ATP synthase (F-ATPase) is found in every domain of life, and is believed to predate the divergence of these lineages over 1.5 billion years ago. These enzymes have therefore facilitated the survival of organisms in a wide range of habitats, ranging from the deep-sea thermal vents to the human intestine. In this review, we present an overview of the current knowledge of the structure and function of F-type ATPases, highlighting several adaptations that have been characterized across taxa. We emphasize the importance of studying these features within the context of the enzyme's particular lipid environment: Just as the interactions between an organism and its physical environment shape its evolutionary trajectory, ATPases are impacted by the membranes within which they reside. We argue that a comprehensive understanding of the structure, function, and evolution of membrane proteins -- including ATP synthase -- requires such an integrative approach.Comment: Review article; 29 pages, 6 figures/1 tabl