The CREC family, a novel family of multiple EF-hand, low-affinity Ca(2+)-binding proteins localised to the secretory pathway of mammalian cells.
(17/1054)
The CREC family consists of a number of recently discovered multiple (up to seven) EF-hand proteins that localise to the secretory pathway of mammalian cells. At present, the family includes reticulocalbin, ERC-55/TCBP-49/E6BP, Cab45, calumenin and crocalbin/CBP-50. Similar proteins are found in quite diverse invertebrate organisms such as DCB-45 and SCF in Drosophila melanogaster, SCF in Bombyx mori, CCB-39 in Caenorhabditis elegans and Pfs40/PfERC in Plasmodium falciparum. The Ca(2+) affinity is rather low with dissociation constants around 10(-4)-10(-3) M. The proteins may participate in Ca(2+)-regulated activities. Recent evidence has been obtained that some CREC family members are involved in pathological activities such as malignant cell transformation, mediation of the toxic effects of snake venom toxins and putative participation in amyloid formation. (+info)
The molecular biology of invertebrate voltage-gated Ca(2+) channels.
(18/1054)
The importance of voltage-gated Ca(2+) channels in cellular function is illustrated by the many distinct types of Ca(2+) currents found in vertebrate tissues, a variety that is generated in part by numerous genes encoding Ca(2+) channel subunits. The degree to which this genetic diversity is shared by invertebrates has only recently become apparent. Cloning of Ca(2+) channel subunits from various invertebrate species, combined with the wealth of information from the Caenorhabditis elegans genome, has clarified the organization and evolution of metazoan Ca(2+) channel genes. Functional studies have employed novel structural information gained from invertebrate Ca(2+) channels to complement ongoing research on mammalian Ca(2+) currents, while demonstrating that the strict correspondence between pharmacological and molecular classes of vertebrate Ca(2+) channels does not fully extend to invertebrate tissues. Molecular structures can now be combined with physiological data to develop a more cogent system of categorizing invertebrate channel subtypes. In this review, we examine recent progress in the characterization of invertebrate Ca(2+) channel genes and its relevance to the diversity of invertebrate Ca(2+) currents. (+info)
Bilaterian origins: significance of new experimental observations.
(19/1054)
Several recent laboratory observations that bear on the origin of the Bilateria are reviewed and interpreted in light of our set-aside cell theory for bilaterian origins. We first discuss new data concerning the phylogeny of bilaterian phyla. Next, we use systematic, molecular, and paleontological lines of evidence to argue that the latest common ancestor of echinoderms plus hemichordates used a maximal indirect mode of development. Furthermore, the latest common ancestor of molluscs and annelids was also indirectly developing. Finally, we discuss new data on Hox gene expression patterns which suggest that both sea urchins and polychaete annelids use Hox genes in a very similar fashion. Neither utilizes the complete Hox complex in the development of the larva per se, while the Hox complex is expressed in the set-aside cells from which the adult body plan is formed. Our current views on the ancestry of the bilaterians are summarized in phylogenetic terms, incorporating the characters discussed in this paper. (+info)
Salmon antithrombin has only three carbohydrate side chains, and shows functional similarities to human beta-antithrombin.
(20/1054)
Antithrombin, a major coagulation inhibitor in mammals, has for the first time been cDNA cloned from a fish species. The predicted mature liver antithrombin of Atlantic salmon (Salmo salar) consists of 430 amino acids and shows about 67% sequence identity to mammalian and chicken antithrombins. Due to a single nucleotide replacement, Asn135 of the antithrombin in higher vertebrates is substituted by Asp in the salmon homolog. Hence, in contrast to the vertebrate antithrombins known so far, salmon antithrombin lacks the potential glycosylation site located close to the heparin binding site. The existence of only three N-linked side chains is evidenced by the sequential removal of three carbohydrate chains from salmon antithrombin during timed-digestion with N-glycosidase F. The high heparin binding affinity of the salmon inhibitor, Kd of 2.2 and 48 nM at I = 0.15 and 0.3, respectively, is very similar to that of the minor human isoform beta-antithrombin, which is not glycosylated at Asn135. Furthermore, the invariant third-position Ser137 at this glycosylation site of mammalian and chicken antithrombins is substituted by Thr in the salmon, a replacement that has been shown to induce full glycosylation in human antithrombin. Thus a rapidly reacting pool of antithrombin may have evolved in two different ways: absence of a glycosylation site in lower vertebrates vs. incomplete glycosylation of a part of the circulating antithrombin in higher vertebrates. Salmon antithrombin appears to have three complex oligosaccharide side chains containing sialic acid terminally linked alpha(2-3) to galactose, while trace amounts of Galbeta(1-4)GlcNAc suggest microheterogeneity due to partial loss of sialic acid. (+info)
Monophyly of brachiopods and phoronids: reconciliation of molecular evidence with Linnaean classification (the subphylum Phoroniformea nov.).
(21/1054)
Molecular phylogenetic analyses of aligned 18S rDNA gene sequences from articulate and inarticulate brachiopods representing all major extant lineages, an enhanced set of phoronids and several unrelated protostome taxa, confirm previous indications that in such data, brachiopod and phoronids form a well-supported clade that (on previous evidence) is unambiguously affiliated with protostomes rather than deuterostomes. Within the brachiopod-phoronid clade, an association between phoronids and inarticulate brachiopods is moderately well supported, whilst a close relationship between phoronids and craniid inarticulates is weakly indicated. Brachiopod-phoronid monophyly is reconciled with the most recent Linnaean classification of brachiopods by abolition of the phylum Phoronida and rediagnosis of the phylum Brachiopoda to include tubiculous, shell-less forms. Recognition that brachiopods and phoronids are close genealogical allies of protostome phyla such as molluscs and annelids, but are much more distantly related to deuterostome phyla such as echinoderms and chordates, implies either (or both) that the morphology and ontogeny of blastopore, mesoderm and coelom formation have been widely misreported or misinterpreted, or that these characters have been subject to extensive homoplasy. This inference, if true, undermines virtually all morphology-based reconstructions of phylogeny made during the past century or more. (+info)
Extracellular matrix (ECM) components in a very primitive multicellular animal, the dicyemid mesozoan Kantharella antarctica.
(22/1054)
One of the most vital synapomorphic properties of metazoans is the presence of an extracellular matrix (ECM), i.e., a complex of proteoglycans, adhesive glycoproteins, and collagens. The genetically controlled ECM mediates between the respective receptors morphogenesis and cell differentiation and is central to gastrulation, i.e., the process which generates the embryonic germ layers, upon which all metazoan body structures are based. However, the primitive metazoans include a phylum, viz. the Dicyemida, which lacks any kind of typical metazoan ECM structures including a basement membrane, and hence does not develop through gastrulation. Since the ECM components fibronectin, laminin, and type IV collagen, all of which are essential constituents of each basement membrane, have been proved to be evolutionary ancient molecules from the lowest metazoans up to vertebrates, antibodies against the respective vertebrate ECM components were employed by electron microscopy to look for these molecules also in the dicyemid mesozoan Kantharella antarctica. As a result, all three protein families showed an immunolabel which was localized intracellularly and intimately associated with the cell membranes as well as with the submembranously arranged delicate filamentous network. The immunolabel was most intense in the fibronectin-like protein, followed by the type IV collagen-like protein and weakest in the laminin-like protein. From an evolutionary point of view, this kind of distribution of ECM components, primarily found in intracellular regions, seems to reflect a very primitive situation of the structures of the respective ECM molecules having not yet reached their definitive position outside the cell, thus generating the complete biological function of typical ECM. Moreover, these results confirm the long-standing presumption that the dicyemid mesozoan body structure might be the missing link between the Protozoa and Metazoa. (+info)
Regulatory evolution and the origin of the bilaterians.
(23/1054)
The adult body plan of bilaterians is achieved by imposing regional specifications on pluripotential cells. The establishment of spatial domains is governed in part by regulating expression of transcription factors. The key to understanding bilaterian evolution is contingent on our understanding of how the regulation of these transcription factors influenced bilaterian stem-group evolution. (+info)
The new animal phylogeny: reliability and implications.
(24/1054)
DNA sequence analysis dictates new interpretation of phylogenic trees. Taxa that were once thought to represent successive grades of complexity at the base of the metazoan tree are being displaced to much higher positions inside the tree. This leaves no evolutionary "intermediates" and forces us to rethink the genesis of bilaterian complexity. (+info)