Transport of Cytoplasmically Synthesized Proteins into the Mitochondria in a Cell Free System from Neurospora crassa

Synthesis and transport of mitochondrial proteins were followed in a cell-free homogenate of Neurospora crassa in which mitochondrial translation was inhibited. Proteins synthesized on cytoplasmic ribosomes are transferred into the mitochondrial fraction. The relative amounts of proteins which are transferred in vitro are comparable to those transferred in whole cells. Cycloheximide and puromycin inhibit the synthesis of mitochondrial proteins but not their transfer into mitochondria. The transfer of immunoprecipitable mitochondrial proteins was demonstrated for matrix proteins, carboxyatractyloside-binding protein and cytochrome c. Import of proteins into mitochondria exhibits a degree of specificity. The transport mechanism differentiates between newly synthesized proteins and preexistent mitochondrial proteins, at least in the case of matrix proteins. In the cell-free homogenate membrane-bound ribosomes are more active in the synthesis of mitochondrial proteins than are free ribosomes. The finished translation products appear to be released from the membrane-bound ribosomes into the cytosol rather than into the membrane vesicles. The results suggest that the transport of cytoplasmically synthesized mitochondrial proteins is essentially independent of cytoplasmic translation; that cytoplasmically synthesized mitochondrial proteins exist in an extramitochondrial pool prior to import; that the site of this pool is the cytosol for at least some of the mitochondrial proteins; and that the precursors in the extramitochondrial pool differ in structure or conformation from the functional proteins in the mitochondria

Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology

The best European locality for complete Eocene mammal skeletons is Grube Messel, near Darmstadt, Germany. Although the site was surrounded by a para-tropical rain forest in the Eocene, primates are remarkably rare there, and only eight fragmentary specimens were known until now. Messel has now yielded a full primate skeleton. The specimen has an unusual history: it was privately collected and sold in two parts, with only the lesser part previously known. The second part, which has just come to light, shows the skeleton to be the most complete primate known in the fossil record.We describe the morphology and investigate the paleobiology of the skeleton. The specimen is described as Darwinius masillae n.gen. n.sp. belonging to the Cercamoniinae. Because the skeleton is lightly crushed and bones cannot be handled individually, imaging studies are of particular importance. Skull radiography shows a host of teeth developing within the juvenile face. Investigation of growth and proportion suggest that the individual was a weaned and independent-feeding female that died in her first year of life, and might have attained a body weight of 650-900 g had she lived to adulthood. She was an agile, nail-bearing, generalized arboreal quadruped living above the floor of the Messel rain forest.Darwinius masillae represents the most complete fossil primate ever found, including both skeleton, soft body outline and contents of the digestive tract. Study of all these features allows a fairly complete reconstruction of life history, locomotion, and diet. Any future study of Eocene-Oligocene primates should benefit from information preserved in the Darwinius holotype. Of particular importance to phylogenetic studies, the absence of a toilet claw and a toothcomb demonstrates that Darwinius masillae is not simply a fossil lemur, but part of a larger group of primates, Adapoidea, representative of the early haplorhine diversification

A review of the fossil record of turtles of the clade Pan-Carettochelys

Turtles of the total clade Pan-Carettochelys have a relatively poor fossil record that extends from the Early Cretaceous. The clade is only found in Asia during the Cretaceous, but spreads to Europe and North America during the Eocene. Neogene finds are restricted to Europe, Africa and Australia, whereas the only surviving species, Carettochelys insculpta, lives in New Guinea and the Northern Territories of Australia. The ecology of fossil pan-carettochelyids appears similar to that of the extant C. insculpta, although more primitive representatives were likely less adapted to brackish water. Current phylogenies only recognize three internested clades: Pan- Carettochelys, Carettochelyidae and Carettochelyinae. A taxonomic review of the group concludes that of 25 named taxa, 13 are nomina valida, 7 are nomina invalida, 3 are nomina dubia, and 2 are nomina nuda

A novel μCT analysis reveals different responses of bioerosion and secondary accretion to environmental variability

Corals build reefs through accretion of calcium carbonate (CaCO3) skeletons, but net reef growth also depends on bioerosion by grazers and borers and on secondary calcification by crustose coralline algae and other calcifying invertebrates. However, traditional field methods for quantifying secondary accretion and bioerosion confound both processes, do not measure them on the same time-scale, or are restricted to 2D methods. In a prior study, we compared multiple environmental drivers of net erosion using pre- and post-deployment micro-computed tomography scans (μCT; calculated as the % change in volume of experimental CaCO3 blocks) and found a shift from net accretion to net erosion with increasing ocean acidity. Here, we present a novel μCT method and detail a procedure that aligns and digitally subtracts pre- and post-deployment μCT scans and measures the simultaneous response of secondary accretion and bioerosion on blocks exposed to the same environmental variation over the same time-scale. We tested our method on a dataset from a prior study and show that it can be used to uncover information previously unattainable using traditional methods. We demonstrated that secondary accretion and bioerosion are driven by different environmental parameters, bioerosion is more sensitive to ocean acidity than secondary accretion, and net erosion is driven more by changes in bioerosion than secondary accretion

Thyroid hormone action on mitochondria

Measurements of fluorescence at >420 nm and extracted NADPH in mitochondria obtained from the livers of hypothyroid rats show that the addition of Pi, ADP and glutamate rapidly reduces over 90% of the total reducible intrinsic pyridine nucleotides in State 3, compared with 20% in normals. The total fluorescence intensity change and reducible NADP + is about twice normal in hypothyroid mitochondria. Adding 6–30 µM l -thyroxine to hypothyroid mitochondria in vitro decreases and delays the substrate-induced reduction of pyridine nucleotides, and excludes both NADP + from such reduction and NADPH from oxidation by added ADP + Pi, without changing the high NADP(H) content. The correcting actions of the hormone are rapidly reversed by albumin, probably by binding free hormone. Changes in respiration do not appear to account for these observations. There is indirect evidence for decreased phosphorylation of added ADP in hypothyroid mitochondria, and a correction by added hormone. The hormonal actions on NADP(H) redox reactions are not reproduced by 1 to 6 µM dinitrophenol in vitro . l -Thyroxine appears to specifically block the participation of NADP (H) in redox reactions in mitochondria from hypothyroid rats, perhaps by effecting a sequestration of the nucleotide, by inhibiting the pyridine nucleotide transhydrogenase, or by activating an energy-linked process that competes with transhydrogenation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44803/1/10863_2004_Article_BF00761448.pd

Skeleton of an unusual cat-sized marsupial relative (Metatheria: Marsupialiformes) from the middle Eocene (Lutetian: 44-43 million years ago) of Turkey

We describe a near-complete, three-dimensionally preserved skeleton of a metatherian (relative of modern marsupials) from the middle Eocene (Lutetian: 44–43 million years ago) Lülük member of the Uzunçarşıdere Formation, central Turkey. With an estimated body mass of 3–4 kg, about the size of a domestic cat (Felis catus) or spotted quoll (Dasyurus maculatus), it is an order of magnitude larger than the largest fossil metatherians previously known from the Cenozoic of the northern hemisphere. This new taxon is characterised by large, broad third premolars that probably represent adaptations for hard object feeding (durophagy), and its craniodental morphology suggests the capacity to generate high bite forces. Qualitative and quantitative functional analyses of its postcranial skeleton indicate that it was probably scansorial and relatively agile, perhaps broadly similar in locomotor mode to the spotted quoll, but with a greater capacity for climbing and grasping. Bayesian phylogenetic analysis of a total evidence dataset comprising 259 morphological characters and 9kb of DNA sequence data from five nuclear protein-coding genes, using both undated and “tip-and-node dating” approaches, place the new taxon outside the marsupial crown-clade, but within the clade Marsupialiformes. It demonstrates that at least one metatherian lineage evolved to occupy the small-medium, meso- or hypo-carnivore niche in the northern hemisphere during the early Cenozoic, at a time when there were numerous eutherians (placentals and their fossil relatives) filling similar niches. However, the known mammal fauna from Uzunçarşıdere Formation appears highly endemic, and geological evidence suggests that this region of Turkey was an island for at least part of the early Cenozoic, and so the new taxon may have evolved in isolation from potential eutherian competitors. Nevertheless, the new taxon reveals previously unsuspected ecomorphological disparity among northern hemisphere metatherians during the first half of the Cenozoic

Discovery of cretaceous arboreal eutherians

This article does not have an abstract

Role of phosphate on the ADP-induced hysteretic inhibition of mitochondrial adenosine 5'-triphosphatase. Effects of the natural protein inhibitor.

International audiencePreincubation of F1-ATPase with ADP and Mg2+ leads to ADP binding at regulatory site inducing a hysteretic inhibition of ATP hydrolysis, i.e., an inhibition that slowly develops after Mg-ATP addition (Di Pietro, A., Penin, F., Godinot, C. and Gautheron, D.C. (1980) Biochemistry 19, 5671-5678). It is shown here that inorganic phosphate (Pi) together with ADP during preincubation abolishes the time-dependence of the inhibition after the addition of the substrate Mg-ATP. This preincubation in the presence of both Pi and ADP slowly leads to a conformation of the enzyme immediately inhibited after the addition of the substrate Mg-ATP. The Pi effect is half-maximal at 35 microM and pH 6.6, whereas a limited effect is induced at pH 8.0. The preincubation of F1-ATPase with Pi and ADP must last long enough (t1/2 = 5 min). The effects can be correlated to the amount of Pi bound to the enzyme, 1 mol Pi per mol (apparent KD of 33 microM) at saturation. Pi neither modifies the ADP binding nor the final level of the concomitant inhibition. When Pi is not present in the preincubation, the final stable rate of ADP-induced hysteretic inhibition is always reached when a near-constant amount of Pi has been generated during Mg-ATP hydrolysis. Kinetic experiments indicate that preincubation with ADP and Pi decreases both Vmax and Km which would favor a conformational change of the enzyme. Taking into account the Pi effects, a more precise model of hysteretic inhibition is proposed. The natural protein inhibitor IF1 efficiently prevents the binding of Pi produced by ATP hydrolysis indicating that the hysteretic inhibition and the IF1-dependent inhibition obey different mechanisms.Preincubation of F1-ATPase with ADP and Mg2+ leads to ADP binding at regulatory site inducing a hysteretic inhibition of ATP hydrolysis, i.e., an inhibition that slowly develops after Mg-ATP addition (Di Pietro, A., Penin, F., Godinot, C. and Gautheron, D.C. (1980) Biochemistry 19, 5671-5678). It is shown here that inorganic phosphate (Pi) together with ADP during preincubation abolishes the time-dependence of the inhibition after the addition of the substrate Mg-ATP. This preincubation in the presence of both Pi and ADP slowly leads to a conformation of the enzyme immediately inhibited after the addition of the substrate Mg-ATP. The Pi effect is half-maximal at 35 microM and pH 6.6, whereas a limited effect is induced at pH 8.0. The preincubation of F1-ATPase with Pi and ADP must last long enough (t1/2 = 5 min). The effects can be correlated to the amount of Pi bound to the enzyme, 1 mol Pi per mol (apparent KD of 33 microM) at saturation. Pi neither modifies the ADP binding nor the final level of the concomitant inhibition. When Pi is not present in the preincubation, the final stable rate of ADP-induced hysteretic inhibition is always reached when a near-constant amount of Pi has been generated during Mg-ATP hydrolysis. Kinetic experiments indicate that preincubation with ADP and Pi decreases both Vmax and Km which would favor a conformational change of the enzyme. Taking into account the Pi effects, a more precise model of hysteretic inhibition is proposed. The natural protein inhibitor IF1 efficiently prevents the binding of Pi produced by ATP hydrolysis indicating that the hysteretic inhibition and the IF1-dependent inhibition obey different mechanisms