AtPAP2 is a tail-anchored protein in the outer membrane of chloroplasts and mitochondria

To date, Arabidopsis purple acid phosphatase 2 (AtPAP2) is the only known plant protein that is dual-targeted to chloroplasts and mitochondria by a C-terminal targeting signal. Using in vitro organelle import and green fluorescence protein (GFP) localization assays, we showed that AtPAP2 is located on, but not imported across the outer membrane (OM) of chloroplasts and mitochondria and exposed its N-terminal enzymatic domain to the cytosol. It was also found that a short stretch of 30 amino acids (a.a.) at the C-terminal region (a.a. 615-644) that contains a stretch of 18 hydrophobic residues, a WYAK motif and 8 hydrophilic residues is sufficient for dual-targeting. Mutation of WYAK to WYAE had no effect on dual-targeting ability suggesting that the charge within this flanking region alone is not an important determinant for dual-targeting.        

Characterization of a novel long-chain acyl-CoA thioesterase from Alcaligenes faecalis

A novel long-chain acyl-CoA thioesterase from Alcaligenes faecalis has been isolated and characterized. The protein was extracted from the cells with 1 m NaCl, which required 1.5-fold, single-step purification to yield near-homogeneous preparations. In solution, the protein exists as homomeric aggregates, of mean diameter 21.6 nm, consisting of 22-kDa subunits. MS/MS data for peptides obtained by trypsin digestion of the thiosterase did not match any peptide from Escherichia coli thioesterases or any other thioesterases in the database. The thioesterase was associated exclusively with the surface of cells as revealed by ultrastructural studies using electron microscopy and immunogold labeling. It hydrolyzed saturated and unsaturated fatty acyl-CoAs of C12 to C18 chain length with Vmax and Km of 3.58-9.73 micromol x min(-1) x (mg protein)(-1) and 2.66-4.11 microm, respectively. A catalytically important histidine residue is implicated in the active site of the enzyme. The thioesterase was active and stable over a wide range of temperature and pH. Maximum activity was observed at 65 degrees C and pH 10.5, and varied between 60% and 80% at temperatures of 25-70 degrees C and pH 6.5-10. The thioesterase also hydrolyzed p-nitrophenyl esters of C2 to C12 chain length, but substrate competition experiments demonstrated that the long-chain acyl-CoAs are better substrates for thioesterase than p-nitrophenyl esters. When assayed at 37 and 20 degrees C, the affinity and catalytic efficiency of the thioesterase for palmitoleoyl-CoA and cis-vaccenoyl-CoA were reduced approximately twofold at the lower temperature, but remained largely unaltered for palmitoyl-CoA.     

Diurnal surface concentrations of zooplankton in Lake Taupo,New Zealand

Summary The planktonic speciesBoekella propinqua, Bosmina meridionalis, andCeriodaphnia dubia were found to rise to the surface waters of Lake Taupo in peak concentrations approximately two hours after sunset; the time of the rise varying according to the season.B. propinqua made a rapid descent from the surface, but this was not so marked for the other two species. None of the species rose to the surface at dawn. This form of behaviour differs from the migration pattern of similar species in other lakes in New Zealand, and the conclusion is drawn that the depth and transparency of lakes influence the rhythm of migration.

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Résumé Les espèces planctoniquesBoeckella propinqua, Bosmina meridionalis etCeriodaphnia dubia sont trouvés à monter à la surface de l'eau du lac Taupo dans des concentrations maximales presque deux heures après le coucher du soleil; le temps de l'ascension variant avec la saison.B. propinqua descend vite de la surface mais cela n'est pas si marquant pour les deux autres espèces. Aucun des espèces montait à la surface à l'aube. Cette forme de conduite diffère de la mode de migration des espèces semblables dans d'autres lacs et la conclusion est faite que le profondeur et la transparence influencent le rythme de migration.

     

Comparison of unipedicled and bipedicled TRAM flap breast reconstructions: assessment of physical function and patient satisfaction

Many variations of the transverse rectus abdominis musculocutaneous (TRAM) flap breast reconstruction have been attempted since the procedure was first described. One common modification involves the use of both rectus muscles, which may accommodate a bilateral reconstruction or provide a more reliable blood supply to a unilateral reconstruction. Objective studies measuring various aspects of physical strength after bilateral rectus harvest and subjective reports of various physical symptoms have challenged the morbidity of a double-rectus harvest. Whether this represents increased morbidity in practical terms is best clarified by asking the patients. To answer this question, 124 TRAM flap reconstruction patients (62 unipedicled patients and 62 bipedicled patients) completed a survey containing questions regarding postoperative physical activities and abilities, outcome with regard to specific physical symptoms, and satisfaction with the procedure. The overwhelming majority of patients reported no untoward effect postoperatively regarding the following: workday performance (>or=90 percent), workday performance involving physical labor (>or=78 percent), physical recreation (>or=77 percent), abdominal appearance (>or=77 percent), standing posture (>or=95 percent), and back pain (>or=81 percent). When comparing unipedicled and bipedicled TRAM patient groups, there was no statistically significant difference between the two groups for any of these criteria. However, a subjective decrease in abdominal muscle strength was reported by 42 percent of unipedicled and 64 percent of bipedicled TRAM flap patients, and decreased abdominal muscle strength was the most frequently cited reason for dissatisfaction. Interestingly, this decreased strength did not affect the daily activities of the majority of patients, who were happy with the procedure (96 percent) and would recommend it to others (96 percent).     

Environmental and scale-dependent evolutionary trends in the body size of crustaceans

The ecological and physiological significance of body size is well recognized. However, key macroevolutionary questions regarding the dependency of body size trends on the taxonomic scale of analysis and the role of environment in controlling long-term evolution of body size are largely unknown. Here, we evaluate these issues for decapod crustaceans, a group that diversified in the Mesozoic. A compilation of body size data for 792 brachyuran crab and lobster species reveals that their maximum, mean and median body size increased, but no increase in minimum size was observed. This increase is not expressed within lineages, but is rather a product of the appearance and/or diversification of new clades of larger, primarily burrowing to shelter-seeking decapods. This argues against directional selective pressures within lineages. Rather, the trend is a macroevolutionary consequence of species sorting: preferential origination of new decapod clades with intrinsically larger body sizes. Furthermore, body size evolution appears to have been habitat-controlled. In the Cretaceous, reef-associated crabs became markedly smaller than those in other habitats, a pattern that persists today. The long-term increase in body size of crabs and lobsters, coupled with their increased diversity and abundance, suggests that their ecological impact may have increased over evolutionary time.