ATPase

During Pleistocene, the Laurentide ice sheet rearranged and diversified biotic distributions in eastern North America, yet had minimal physical impact in western North America where lineage diversification is instead hypothesized to result from climatic changes. If Pleistocene climatic fluctuations impacted desert species, the latter would reflect patterns of restricted gene flow concomitant with indications of demographic bottlenecks. Accordingly, molecular evidence for refugia should be present within these distributions and for subsequent range expansions as conditions improved. We sought answers to these questions by evaluating mitochondrial DNA (mtDNA) sequences from four species of rattlesnakes [ Crotalus mitchellii (speckled rattlesnake), Crotalus cerastes (sidewinder), Crotalus tigris (tiger rattlesnake), Crotalus ruber (red diamond rattlesnake)] with distributions restricted to desert regions of southwestern North America. We inferred relationships using parsimony and maximum likelihood, tested intraspecific clades for population expansions, applied an isolation-with-migration model to determine bi-directional migration rates ( m ) among regions, and inferred divergence times for species and clades by applying a semiparametric penalized likelihood approach to our molecular data. Evidence for significant range expansion was present in two of eight regions in two species ( Crotalus mitchellii pyrrhus , C. tigris region north). Two species ( C. cerastes , C. mitchellii ) showed a distribution concomitant with northward displacement of Baja California from mainland México, followed by vicariant separation into subclades. Effects of Pleistocene climate fluctuations were found in the distributions of all four species. Three regional diversification patterns were identified: (i) shallow genetic diversity that resulted from Pleistocene climatic events ( C. tigris, C. ruber ); (ii) deep Pleistocene divisions indicating allopatric segregation of subclades within refugia ( C. mitchellii, C. cerastes) ; and (iii) lineage diversifications that extended to Pliocene or Late Miocene ( C. mitchellii, C. cerastes) . Clade-diversifying and clade-constraining effects impacted the four species of rattlesnakes unequally. We found relatively high levels of molecular diversification in the two most broadly distributed species ( C. mitchellii, C. cerastes ), and lower levels of genetic diversification in the two species ( C. tigris, C. ruber ) whose ranges are relatively more restricted. Furthermore, in several cases, the distributions of subspecies were not congruent with our molecular information. We suggest regional conservation perspectives for southwestern deserts cannot rely upon subspecies as biodiversity surrogates, but must instead employ a molecular and deep historical perspective as a primary mechanism to frame biodiversity reserves within this region.

Mitochondrial DNA ( mtDNA) sequences of the marbled hatchetfish Carnegiella strigata, an ornamental fish exported from the Negro River, was examined to determine its genetic diversity and population structure in blackwater rivers (Negro and Uatumã Rivers) in the central Amazon. Analyses of a 646 bp fragment of the ATPase 6/8 mtDNA gene revealed two monophyletic lineages of C. strigata with considerable genetic distance between them (10-12%), suggesting that these lineages should not be considered a single stock. Furthermore, there were strong differences in the geographical distribution of the lineages. These results indicate a past association between drainages of the Negro and Uatumã Rivers. They also suggest that, in the Negro River, its main tributary, the Branco River, may act as a geographical barrier and potentially an ecological barrier between populations of the middle and lower portions of the river.

RNA helicases of the DEAD-box protein family have been shown to participate in every aspect of RNA metabolism. They are present in most organisms where they work as RNA helicases or RNPases. The properties of these enzymes in vivo remains poorly described, however some were extensively characterized in vitro, and the solved crystal structures of a few are now available. Taken together, this information gives insight into the regulation of ATP and RNA binding as well as in the ATPase and helicase activities. This review will focus on the description of the molecular characteristics of members of the DEAD-box protein family and on the enzymatic activities they possess.

In this paper we present the inhibitory effect of a variety of structurally modulated/modified polyphenolic compounds on purified F 1 or membrane bound F 1 F o Escherichia coli ATP synthase. Structural modulation of polyphenols with two phenolic rings inhibited ATP synthase essentially completely; one or three ringed polyphenols individually or fused together inhibited partially. We found that the position of hydroxyl and nitro groups plays critical role in the degree of binding and inhibition of ATPase activity. The extended positioning of hydroxyl groups on imino diphenolic compounds diminished the inhibition and abridged position enhanced the inhibition potency. This was contrary to the effect by simple single ringed phenolic compounds where extended positioning of hydroxyl group was found to be effective for inhibition. Also, introduction of nitro group augmented the inhibition on molar scale in comparison to the inhibition by resveratrol but addition of phosphate group did not. Similarly, aromatic diol or triol with rigid or planar ring structure and no free rotation poorly inhibited the ATPase activity. The inhibition was identical in both F 1 F o membrane preparations as well as in isolated purified F 1 and was reversible in all cases. Growth assays suggested that modulated compounds used in this study inhibited F 1-ATPase as well as ATP synthesis nearly equally.

Ca 2 +-ATPase activity was measured in electric organ synaptosomal homogenates and their derived presynaptic plasma membranes using a low ionic strength medium, low in Ca 2÷ and Mg 2÷, and devoid of K +. The enzyme activity showed a high apparent affinity for Ca 2+ (Kca:0.5 pM) and was: (1) 5-fold stimulated by 120 nM calmodulin, (2) highly sensitive to LaC! 3 inhibition, and (3) not affected by 20 mM NaN 3 or 0.1 mM ouahain. The addition of Mg 2+ promoted the disappearance of Ca2+-ATPase activity. Incubation of synaptosomal homogenates in the above-mentioned assay medium with h,-32p]ATP resulted in the appearance of a 140 kDa band as revealed by SDS-gel electrophoresis. Labeling of this band with 32p was inhibited by 1 mM EGTA or 10 mM NH2OI-I, indicating that the isotope incorporation required the presence of Ca 2+ and the formation of an acyl-phosphate derivative. The results indicate that the Ca2+-ATPase activity from synaptosomal homogenates had characteristics corresponding to those of the enzyme that catalyzes an outward transport of Ca 2÷ in nerve terminals. Preincubation of synaptosomes in Ca 2+ plus K ÷, a depolarizing procedure, induced a large and rapid decrease in the Ca2+-ATPase activity, possibly mediated via Ca 2÷ entry through voltage-gated Ca z+ channels. Furthermore, the muscarinic cholinergic agonist oxotremorine (at 15/~M concentration) did not significantly affect either the enzyme activity or the intensity of the Ca2+-dependent 32p incorporation into the 140 kDa band, suggesting that the enzyme is not coupled to muscarinic binding sites. electrochemical potential gradient. The axoplasmic free Ca 2÷ concentration suddenly increases initiating a series of events which culminate with the liberation of the neurotransmitter acetylcholine .

W e cloned and sequenced the chloroplast atpB/E gene cluster encoding the 8and esubunits of the chloroplast ATPase, together with itsjlanking regions, in the centric diatom Odontella sinensis (Grev.) Grunow. This gene cluster, which was transcribed into a main transcript of 3.5 kb, was Janked by the genes ycf 3 (upstream atpB) and ORF 263 (downstream atpE), the latter being un-I