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Cytochrome c release from the mitochondria is a critical component of the apoptotic cell-death program. Cytochrome c–catalyzed peroxidation of cardiolipin, a mitochondrial phospholipid, has now been shown to lessen the binding of cytochrome c to the mitochondrial inner membrane and facilitate permeabilization of the outer membrane. These results describe a new and earlier pro-apoptotic role for cytochrome c.
Blocking gene expression by interfering with translation of mRNA can be accomplished by means of antisense or short interfering RNA strategies, but more potent inhibitors would act by inhibiting transcription of genomic DNA. Two new studies show efficient inhibition of transcription using single-stranded peptide nucleic acid or double-stranded RNA targeted to the open complex formed at the transcription start site.
Examples abound in nature in which organisms adapt and optimize their fitness in a given environment. A new study demonstrates that a cellular cost-benefit analysis drives growth optimization over the course of evolution by attenuation of protein expression levels.
Voltage-gated ion channels respond to alterations in membrane potential and mediate action potential in neurons. A recent study provides new insights into the structure and gating of the Shaker potassium channel.
Iron-sulfur clusters and hemes are two iron-containing prosthetic groups involved in important physiological functions. Identification of the gene responsible for anemia in a mutant zebrafish has revealed an unexpected link between iron-sulfur cluster assembly and heme synthesis in red blood cells.
Near-field scanning optical microscopy has been used to study the organization of β1- and β2-adrenergic receptors in cardiac cells. The fluorescently labeled receptors organize into distinct clusters, which may represent localization in microdomains such as lipid rafts and caveolae.