Lectin-like proteins in model organisms: implications for evolution of carbohydrate-binding activity.
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Classes of intracellular lectins that recognize core-type structures and mediate intracellular glycoprotein trafficking are present in vertebrates, model invertebrates such as Caenorhabditis elegans and Drosophila melanogaster, plants, and yeasts. Lectins that recognize more complex structures at the cell surface, such as C-type lectins and galectins, are also found in invertebrate organisms as well as vertebrates, but the functions of these proteins have evolved differently in different animal lineages. (+info)
Properties of the C-terminal domain of 4.1 proteins.
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At the C-terminus of all known 4.1 proteins is a sequence domain unique to these proteins, known as the C-terminal domain (CTD). Mammalian CTDs are associated with a growing number of protein-protein interactions, although such activities have yet to be associated with invertebrate CTDs. Mammalian CTDs are generally defined by sequence alignment as encoded by exons 18-21. Comparison of known vertebrate 4.1 proteins with invertebrate (Caenorhabditis elegans and Drosophila melanogaster) 4.1 proteins indicates that mammalian 4.1 exon 19 represents a vertebrate adaptation that extends the sequence of the CTD with a Ser/Thr-rich sequence. The CTD was first described as a 22/24-kDa domain by chymotryptic digestion of erythrocyte 4.1 (4.1R) [Leto, T.L. & Marchesi, V.T. (1984) J. Biol. Chem. 259, 4603-4608]. Here we show that in 4.1R the 22/24-kDa fragment is not stable but rapidly processed to a 15-kDa fragment by chymotrypsin. The 15-kDa fragment is extremely stable, being resistant to overnight digestion in chymotrypsin on ice. Analysis of this fragment indicates that it is derived from residues 709-858 (SwissProt accession no. P48193), and represents the CTD of 4.1R. The fragment behaves as a globular monomer in solution. Secondary-structure predictions indicate that this domain is composed of five or six beta strands with an alpha helix before the most C-terminal of these. Together these data indicate that the CTD probably represents an independent folding structure which has gained function since the divergence of vertebrates from invertebrates. (+info)
Neuroendocrine secretory protein 7B2: structure, expression and functions.
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7B2 is an acidic protein residing in the secretory granules of neuroendocrine cells. Its sequence has been elucidated in many phyla and species. It shows high similarity among mammals. A Pro-Pro-Asn-Pro-Cys-Pro polyproline motif is its most conserved feature, being carried by both vertebrate and invertebrate sequences. It is biosynthesized as a precursor protein that is cleaved into an N-terminal fragment and a C-terminal peptide. In neuroendocrine cells, 7B2 functions as a specific chaperone for the proprotein convertase (PC) 2. Through the sequence around its Pro-Pro-Asn-Pro-Cys-Pro motif, it binds to an inactive proPC2 and facilitates its transport from the endoplasmic reticulum to later compartments of the secretory pathway where the zymogen is proteolytically matured and activated. Its C-terminal peptide can inhibit PC2 in vitro and may contribute to keep the enzyme transiently inactive in vivo. The PC2-7B2 model defines a new neuroendocrine paradigm whereby proteolytic activation of prohormones and proneuropeptides in the secretory pathway is spatially and temporally regulated by the dynamics of interactions between converting enzymes and their binding proteins. Interestingly, unlike PC2-null mice, which are viable, 7B2-null mutants die early in life from Cushing's disease due to corticotropin ('ACTH') hypersecretion by the neurointermediate lobe, suggesting a possible involvement of 7B2 in secretory granule formation and in secretion regulation. The mechanism of this regulation is yet to be elucidated. 7B2 has been shown to be a good marker of several neuroendocrine cell dysfunctions in humans. The possibility that anomalies in its structure and expression could be aetiological causes of some of these dysfunctions warrants investigation. (+info)
Specific inhibition of gene expression by small double-stranded RNAs in invertebrate and vertebrate systems.
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Short interfering RNAs (siRNAs) are double-stranded RNAs of approximately 21-25 nucleotides that have been shown to function as key intermediaries in triggering sequence-specific RNA degradation during posttranscriptional gene silencing in plants and RNA interference in invertebrates. siRNAs have a characteristic structure, with 5'-phosphate/3'-hydroxyl ends and a 2-base 3' overhang on each strand of the duplex. In this study, we present data that synthetic siRNAs can induce gene-specific inhibition of expression in Caenorhabditis elegans and in cell lines from humans and mice. In each case, the interference by siRNAs was superior to the inhibition of gene expression mediated by single-stranded antisense oligonucleotides. The siRNAs seem to avoid the well documented nonspecific effects triggered by longer double-stranded RNAs in mammalian cells. These observations may open a path toward the use of siRNAs as a reverse genetic and therapeutic tool in mammalian cells. (+info)
Pseudoalteromonas ulvae sp. nov., a bacterium with antifouling activities isolated from the surface of a marine alga.
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A dark-purple marine bacterium that inhibits the germination of marine algal spores and the settlement of invertebrate larvae has been characterized and assessed for taxonomic assignment. Two strains, designated UL12T and UL13, were isolated from the surface of the common marine alga Ulva lactuca. Based on 16S rDNA sequencing, UL12T and UL13 were found to show the highest similarity (97%) to members of the genus Pseudoalteromonas. DNA-DNA hybridization studies demonstrated less than 28% genomic DNA relatedness between these isolates and closely related Pseudoalteromonas species and greater than 65% homology between UL12T and UL13. The two isolates were found to display identical characteristics and are strict aerobes, motile by means of single polar flagella, exhibit non-fermentative metabolism and require sodium ions for growth. The isolates hydrolyse gelatin and can utilize citrate, maltose, mannose and glucose but not trehalose, sucrose, fructose, lactose or glycerol as sole carbon sources. The molecular evidence together with the phenotypic characteristics show that this bacterium constitutes a new species within the genus Pseudoalteromonas. The name Pseudoalteromonas ulvae sp. nov. is proposed for this bacterium and the type strain is UL12T (= UNSW 095600T = NCIMB 13762T). (+info)
The complete mitochondrial genome of the articulate brachiopod Terebratalia transversa.
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We sequenced the complete mitochondrial DNA (mtDNA) of the articulate brachiopod Terebratalia transversa. The circular genome is 14,291 bp in size, relatively small compared with other published metazoan mtDNAs. The 37 genes commonly found in animal mtDNA are present; the size decrease is due to the truncation of several tRNA, rRNA, and protein genes, to some nucleotide overlaps, and to a paucity of noncoding nucleotides. Although the gene arrangement differs radically from those reported for other metazoans, some gene junctions are shared with two other articulate brachiopods, Laqueus rubellus and Terebratulina retusa. All genes in the T. transversa mtDNA, unlike those in most metazoan mtDNAs reported, are encoded by the same strand. The A+T content (59.1%) is low for a metazoan mtDNA, and there is a high propensity for homopolymer runs and a strong base-compositional strand bias. The coding strand is quite G+T-rich, a skew that is shared by the confamilial (laqueid) species L. rubellus but is the opposite of that found in T. retusa, a cancellothyridid. These compositional skews are strongly reflected in the codon usage patterns and the amino acid compositions of the mitochondrial proteins, with markedly different usages being observed between T. retusa and the two laqueids. This observation, plus the similarity of the laqueid noncoding regions to the reverse complement of the noncoding region of the cancellothyridid, suggests that an inversion that resulted in a reversal in the direction of first-strand replication has occurred in one of the two lineages. In addition to the presence of one noncoding region in T. transversa that is comparable with those in the other brachiopod mtDNAs, there are two others with the potential to form secondary structures; one or both of these may be involved in the process of transcript cleavage. (+info)
Biodiversity assessment of benthic macroinvertebrates in altitudinal lotic ecosystems of Serra do Cipo (MG, Brazil).
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Five lotic systems of Serra do Cipo, south-east Brazil, were investigated in order to assess the existing diversity of benthic macroinvertebrates, habitats-microhabitats, and the available trophic resources. For each river it was analysed the communities of benthic macroinvertebrates and the composition of some taxonomic groups (Plecoptera, Ephemeroptera, Trichoptera and Diptera Chironomidae): the community with Bivalvia Sphaeriidae, Oligochaeta and Ephemeroptera Baetidae (being supposed a closed relation Bivalvia-Oligochaeta based on the process of bioturbation and enrichment of sediment in organic matter) in Tanque River; the macrofauna associated to aquatic macrophytes from rivers Peixe and Preto do Itambe reflecting the reaction of the ecosystems versus the quantities of nutrients which originate from the farmlands; the lithoreophilic communities of Cipo River; the community depending on deposits of leaves and filamentous algae in Congonhas Stream; the very rich community of the moss clumps in the Indaia Stream. A proposal for biological zonation of Cipo River and some comments about the importance of the analysed benthic macroinvertebrates in the biological production of the aquatic communities were done. (+info)
Habitat diversity and benthic functional trophic groups at Serra do Cipo, Southeast Brazil.
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The assessment of the diversity of habitats and the characterisation of the functional trophic groups of benthic macroinvertebrate communities of some rivers of Serra do Cipo (MG) were the main objectives of this study. The available trophic resources and the types of substrata were characterised along with the structure and composition of their using functional trophic groups. Serra do Cipo is a watershed divisor of the Sao Francisco and Doce River basins, including a series of streams and rivers, of good water quality and well preserved ecological characteristics. Samples were collected in Cipo, Peixe and Preto do Itambe rivers, besides the Indaia and Capao da Mata streams at 26 sampling stations, during the rainy (February) and dry (October) seasons of 1998, using "Kicking nets" of 0.125 mm mesh size. The group of collectors (Baetidae, Leptophlebiidae and Leptohyphidae) was the most abundant, followed by collector-predators (Hydrophilidae, Ceratopogonidae, Chironomidae-Tanypodinae), and detritivorous-herbivores (Oligochaeta). The riparian vegetation, together with the aquatic macrophytes, are the substrata containing the highest richness of functional trophic groups and the higher habitat diversity. The results suggest that the use of functional trophic groups, together with habitat evaluation, are efficient tools in the evaluation of the diversity of benthic macroinvertebrates, particularly in altitudinal lotic ecosystems. (+info)