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  • Key words: Carbamoyltransferases — ATCase — OTCase — Protein evolution — Gene duplication — Paralogous proteins — Last universal common ancestor — Molecular phylogeny  (1)
  • cationic lipid  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    The Evolutionary History of Carbamoyltransferases: A Complex Set of Paralogous Genes Was Already Present in the Last Universal Common Ancestor (1999)
    Springer
    Journal of molecular evolution 49 (1999), S. 461-473 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Carbamoyltransferases — ATCase — OTCase — Protein evolution — Gene duplication — Paralogous proteins — Last universal common ancestor — Molecular phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Forty-four sequences of ornithine carbamoyltransferases (OTCases) and 33 sequences of aspartate carbamoyltransferases (ATCases) representing the three domains of life were multiply aligned and a phylogenetic tree was inferred from this multiple alignment. The global topology of the composite rooted tree (each enzyme family being used as an outgroup to root the other one) suggests that present-day genes are derived from paralogous ancestral genes which were already of the same size and argues against a mechanism of fusion of independent modules. A closer observation of the detailed topology shows that this tree could not be used to assess the actual order of organismal descent. Indeed, this tree displays a complex topology for many prokaryotic sequences, with polyphyly for Bacteria in both enzyme trees and for the Archaea in the OTCase tree. Moreover, representatives of the two prokaryotic Domains are found to be interspersed in various combinations in both enzyme trees. This complexity may be explained by assuming the occurrence of two subfamilies in the OTCase tree (OTC α and OTC β) and two other ones in the ATCase tree (ATC I and ATC II). These subfamilies could have arisen from duplication and selective losses of some differentiated copies during the successive speciations. We suggest that Archaea and Eukaryotes share a common ancestor in which the ancestral copies giving the present-day ATC II/OTC β combinations were present, whereas Bacteria comprise two classes: one containing the ATC II/OTC α combination and the other harboring the ATC I/OTC β combination. Moreover, multiple horizontal gene transfers could have occurred rather recently amongst prokaryotes. Whichever the actual history of carbamoyltransferases, our data suggest that the last common ancestor to all extant life possessed differentiated copies of genes coding for both carbamoyltransferases, indicating it as a rather sophisticated organism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006569
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  • 2
    Electronic Resource
    Electronic Resource
    Self-Assembling DNA-Lipid Particles for Gene Transfer (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 190-196 
    Details
    ISSN: 1573-904X
    Keywords: gene transfer ; cationic lipid ; DNA complexes ; hydrophobic effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. We have demonstrated that a heteromolecular complex consisting of cationic lipids and DNA can be prepared and isolated (1). Cationic lipids bind DNA through electrostatic interactions. However, when sufficient lipids are bound to DNA the physical and chemical properties of the complex are governed by hydrophobic effects. Here we describe an approach where this hydrophobic complex is used as an intermediate in the preparation of lipid-DNA particles (LDPs). Methods. The approach relies on the generation of mixed micelles containing the detergent, n-octyl β-D-glucopyranoside (OGP), the cationic lipid, N-N-dioleoyl-N, N-dimethylammonium chloride (DODAC), and selected zwitterionic lipids, 1,2-dioleoyl-sn-glycero-3 -phosphoethanolamine (DOPE) or egg sphingomyelin (SM). Results. When these micelles were prepared at low detergent concentrations (20 mM OGP) and combined with pCMVβ DNA, LDPs spontaneously formed. The mean diameter of these particles as measured by quasielastic light scattering was 55−70 nm, a result that was confirmed by negative stain electron microscopy. Further characterization of these LDPs showed that DNA within the particles was inaccessible to the small fluorochrome TO-PRO-1 and protected against DNase I degradation. LDPs could also be prepared in high concentrations of OGP (100 mM), however particles formed only after removal of OGP by dialysis. Particles formed in this manner were large (〉2000nm) and mediated efficient transfection of Chinese hamster ovary cells. Transfection activity was greater when the lipid composition used consisted of SM/ DODAC. Small particles (〈100nm) prepared of SM/DODAC were, however, inefficient transfecting agents. Conclusions. We believe that LDP formation is a consequence of the molecular forces that promote optimal hydrocarbon-hydrocarbon interactions and elimination of the hydrocarbon-water interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012000711033
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    Paper (German National Licenses)
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