Catálogo de publicaciones - revistas

<jats:p> The cell division cycle gene, <jats:italic>CDC34</jats:italic> , is required for ubiquitin-mediated degradation of G <jats:sub>1</jats:sub> regulators and cell cycle progression through the transition from G <jats:sub>1</jats:sub> to S phase in budding yeast. A <jats:italic>CDC34</jats:italic> requirement for S phase onset in higher eukaryotes has not been established. Studies of the simple embryonic cell cycle of <jats:italic>Xenopus laevis</jats:italic> eggs demonstrated that Cdc34p in a large molecular size complex was required in the initiation of DNA replication. Cdc34p appears to regulate the initiation function of Cdk2–cyclin E, perhaps through the degradation of the <jats:italic>Xenopus</jats:italic> cdk inhibitor, Xic1. </jats:p>

<jats:p>Lipidic cubic phases provide a continuous three-dimensional bilayer matrix that facilitates nucleation and growth of bacteriorhodopsin microcrystals. The crystals diffract x-rays isotropically to 2.0 angstroms. The structure of this light-driven proton pump was solved at a resolution of 2.5 angstroms by molecular replacement, using previous results from electron crystallographic studies as a model. The earlier structure was generally confirmed, but several differences were found, including loop conformations and side chain residues. Eight water molecules are now identified experimentally in the proton pathway. These findings reveal the constituents of the proton translocation pathway in the ground state.</jats:p>

<jats:p>Protein folding in the endoplasmic reticulum (ER) often involves the formation of disulfide bonds. The oxidizing conditions required within this organelle were shown to be maintained through the release of small thiols, mainly cysteine and glutathione. Thiol secretion was stimulated when proteins rich in disulfide bonds were translocated into the ER, and secretion was prevented by the inhibition of protein synthesis. Endogenously generated cysteine and glutathione counteracted thiol-mediated retention in the ER and altered the extracellular redox. The secretion of thiols might link disulfide bond formation in the ER to intra- and intercellular redox signaling.</jats:p>

<jats:p>In the developing nervous system, glial cells guide axons to their target areas, but it is unknown whether they help neurons to establish functional synaptic connections. The role of glial cells in synapse formation and function was studied in cultures of purified neurons from the rat central nervous system. In glia-free cultures, retinal ganglion cells formed synapses with normal ultrastructure but displayed little spontaneous synaptic activity and high failure rates in evoked synaptic transmission. In cocultures with neuroglia, the frequency and amplitude of spontaneous postsynaptic currents were potentiated by 70-fold and 5-fold, respectively, and fewer transmission failures occurred. Glial cells increased the action potential–independent quantal release by 12-fold without affecting neuronal survival. Thus, developing neurons in culture form inefficient synapses that require glial signals to become fully functional.</jats:p>