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L Moens

Publications and source records attributed to L Moens.

At least 73 records · Page 4Linked to original sources
PubMed1993

Molecular characterization of an extracellular acid-resistant lipase produced by Rhizopus javanicus.

An extracellular lipase (triacylglycerol acylhydrolase EC 3.1.1.3), produced by the fungus Rhizopus javanicus was purified to homogeneity using an expeditious two-step isolation method. The enzyme, with a molecular mass of 36 kDa and a specific activity of 9260 microequivalent of fatty acid released per minute and mg under standard conditions, consists of three isoforms with isoelectric points of 7.8, 7.7, and 7.1, respectively. The purified lipase was digested using chemical and enzymatical procedures: CNBr cleavage, partial acid hydrolysis, and proteolytic cleavage by means of trypsin. Amino-acid sequencing of the resulting peptides indicates that the three lipases from Rhizopus javanicus, Rhizopus niveus and Rhizopus delemar are produced as identical proenzymes but processed differently. These Rhizopus lipases show 54% identity with the lipase from Rhizomucor miehei. Using the structure of the Rhizomucor miehei lipase, the molecular model of Rhizopus javanicus lipase was constructed. Both enzymes are alpha/beta type proteins with a central 8-stranded mixed beta-pleated sheet and have a remarkably similar distribution of hydrophobic amino acids at their surface. The tryptophan in the center of the helical lid covering the active site of Rhizomucor miehei lipase is mutated into an alanine, indicating that it is not essential for the proper movement of the helical lid.

Amino Acid Sequence↗
PubMed1993

Expression of a globin gene in Caenorhabditis elegans.

Oligonucleotides related to parts of a globin-like sequence in the genome of Caenorhabditis elegans were used to probe a cDNA library from the same species. A complete globin-like sequence was found in the cDNA, showing that a globin gene appears to be expressed. The hypothetical protein was compatible with the conventional globin fold but may be truncated in the B helix, as in Chironomus globin III. An intron in the codon for residue E3 in the E helix was removed in expression. An initiation codon preceded the globin but the sequence upstream (extending for 30 nucleotides to the vector ligation site) had characteristics both of the code for a protein hydrophobic leader and of a trans-spliced RNA leader. The evidence indicates that C. elegans globin has a single domain, unlike some nematodes that express two tandem globin domains in a continuous translation product, and from its sequence may be predicted to have a high affinity for oxygen.

Amino Acid Sequence↗
PubMed1992

Unexpected intron location in non-vertebrate globin genes.

The Caenorhabditis elegans and Artemia T4 globin sequences are highly homologous with other invertebrate globins. The intron/exon patterns of their genes display a single intron in the E and G helices respectively. Precoding introns in multirepeat globins are inserted in homologous positions. Comparison of the intron/exon patterns in the known globin gene sequences demonstrates that they are more diverse than first expected but nevertheless can be derived from an ancestral pattern having 3 introns and 4 exons.

Amino Acid Sequence↗
PubMed1992

Polar zipper sequence in the high-affinity hemoglobin of Ascaris suum: amino acid sequence and structural interpretation.

The extracellular hemoglobin of Ascaris has an extremely high oxygen affinity (P50 = 0.004 mmHg). It consists of eight identical subunits of molecular weight 40,600. Their sequence, determined by protein chemistry, shows two tandemly linked globin-like sequences and an 18-residue C-terminal extension. Two N-linked glycosylation sites contain equal ratios of mannose/glucosamine/fucose of 3:2:1. Electron micrographs suggest that the eight subunits form a polyhedron of point symmetry D4, or 42. The C-terminal extension contains a repeat of the sequence Glu-Glu-His-Lys, which would form a pattern of alternate glutamate and histidine side chains on one side and of glutamate and lysine side chains on the other side of a beta strand. We propose that this represents a polar zipper sequence and that the C-terminal extensions are joined in an eight-stranded beta barrel at the center of the molecule, with histidine and glutamate side chains inside and lysine and glutamate side chains outside the barrel compensating each other's charges. The amino acid sequence of Ascaris hemoglobin fails to explain its high oxygen affinity.

Amino Acid Sequence↗
PubMed1991

The polymeric hemoglobin molecule of Artemia. Interpretation of translated cDNA sequence of nine domains.

Translated cDNA for Artemia hemoglobin provided sequence data for almost nine domains, from the fourth residue of the A helix of one domain through 1405 residues to a stop codon after the ninth domain. The domain sequences were all different (homology between pairs 17-38%) but aligned well with each other and with conventional globins, satisfying the requirements for Phe at CD1, His at F8 and most other highly conserved features of globins including His at E7. Features found to be characteristic of Artemia globin and present in all nine domains were Phe at B10, Tyr at C4, Gly at F5, Phe at G5 and Gly at H22. Approximately 14 residues including a consensus -Val-Asp-Pro-Val-Thr-Gly-Leu- were available to form the linker between each pair of domains. The Artemia sequence data were compared with the crystal structures of Chironomus thummi thummi erythrocruorin III and sperm whale myoglobin in order to identify features of structural similarity and to examine the consequences of the differences. The Artemia sequences were compatible with the main helices and critical features of the globin fold. Possible modifications to the C helix, FG turn, and GH turn were studied in terms of molecular coordinates.

Amino Acid Sequence↗
PubMed1990

Structural interpretation of the amino acid sequence of a second domain from the Artemia covalent polymer globin.

Artemia has a complex extracellular hemoglobin of Mr 260,000 comprising two globin chains (Mr 130,000) each of which is a polymer of eight covalently linked domains of Mr 16,000. The primary structure of this polymeric globin was studied to understand how globin folded domains are ordered within a globin chain and, in turn, how the latter associate into a functional hemoglobin molecule. Here we report the amino acid sequence of a second domain, E7 (Mr 16,081, excluding the heme), and interpretations of sequence data by computer-assisted alignment and modeling. This clearly shows that, as with domain E1 (Moens, L., Van Hauwaert, M.-L., De Smet, K., Geelen, D., Verpooten, G., Van Beeumen, J., Wodak, S., Alard, P., & Trotman, C. (1988) J. Biol. Chem. 263, 4679-4685), domain E7 is compatible with a globin folded structure of the beta-type chain. Several specific differences of domains E7 and E1 from the classic globins are identified. They possibly can be interpreted in terms of specific requirements for a double octameric functional molecule.

Amino Acid Sequence↗
PubMed1988

A structural domain of the covalent polymer globin chains of artemia. Interpretation of amino acid sequence data.

Artemia is unusual in having extracellular hemoglobins of Mr 260,000 comprising two globin chains (Mr 130,000), each of which is a polymer of eight covalently linked domains of about Mr 16,000. The amino acid sequence of one of these domains (E1) has been determined. It has 147 residues and Mr of 17,574 including heme. Sequence alignment revealed 19.0% identity with sperm whale myoglobin, whereas other vertebrate and invertebrate globins had between 13 and 24% identity. However, a much higher percentage of residues has a similar side chain character, suggesting that the domain E1 is very similar to other globins in showing the myoglobin fold. Template model building based on the known three-dimensional structure of myoglobin further supports this conclusion. Conversely, the differences between E1 and other globins are believed to reflect differences in the packing of the domains, first in a covalent polymeric subunit containing eight hemes and subsequently by association of two of these subunits as dimers. These findings provide further evidence for the versatility of the myoglobin fold.

Amino Acid Sequence↗
PubMed1988

An evolutionary tree for invertebrate globin sequences.

A phylogenetic tree was constructed from 245 globin amino acid sequences. Of the six plant globins, five represented the Leguminosae and one the Ulmaceae. Among the invertebrate sequences, 7 represented the phylum Annelida, 13 represented Insecta and Crustacea of the phylum Arthropoda, and 6 represented the phylum Mollusca. Of the vertebrate globins, 4 represented the Agnatha and 209 represented the Gnathostomata. A common alignment was achieved for the 245 sequences using the parsimony principle, and a matrix of minimum mutational distances was constructed. The most parsimonious phylogenetic tree, i.e., the one having the lowest number of nucleotide substitutions that cause amino acid replacements, was obtained employing clustering and branch-swapping algorithms. Based on the available fossil record, the earliest split in the ancestral metazoan lineage was placed at 680 million years before present (Myr BP), the origin of vertebrates was placed at 510 Myr BP, and the separation of the Chondrichthyes and the Osteichthyes was placed at 425 Myr BP. Local "molecular clock" calculations were used to date the branch points on the descending branches of the various lineages within the plant and invertebrate portions of the tree. The tree divided the 245 sequences into five distinct clades that corresponded exactly to the five groups plants, annelids, arthropods, molluscs, and vertebrates. Furthermore, the maximum parsimony tree, in contrast to the unweighted pair group and distance Wagner trees, was consistent with the available fossil record and supported the hypotheses that the primitive hemoglobin of metazoans was monomeric and that the multisubunit extracellular hemoglobins found among the Annelida and the Arthropoda represent independently derived states.

Amino Acid Sequence↗
PubMed1985

The structure of Artemia sp. (brine shrimp) haemoglobins. Purification of a structural unit to homogeneity.

The extracellular haemoglobins (Mr 260 000) of the brine shrimp Artemia sp. were cleaved by limited digestion with subtilisin. Structural units of Mr 16 000, which can bind dioxygen reversibly, were isolated. Analysis of the 16 000-Mr fraction (E) reveals the presence of a limited number of structural units. A single type of structural unit, E1 (Mr 15 800; pI4.8), was purified to homogeneity and characterized.

Amino Acids↗
PubMed1984

The structure of Artemia sp. haemoglobin. Cleavage of the native molecules into functional units by limited subtilisin digestion.

Limited subtilisin digestion of the high-Mr haemoglobin of the crustacean Artemia sp. results in a series of fragments that are multiples of Mr 16000. Properties such as amino acid composition, iron content, absorption and c.d. spectra of the 16000-Mr functional units strongly resemble those of the intact haemoglobin molecules. The 16000-Mr functional units can bind O2 in a non-co-operative way. They thus represent the structural units from which the globin chains are built up.

Amino Acids↗
PubMed1984

cis-Canthaxanthins. Unusual carotenoids in the eggs and the reproductive system of female brine shrimp artemia.

The significance of carotenoid accumulation in crustacean eggs remains obscure, particularly because neither eggs nor female animals have been found to display specific pigment patterns in relation to reproduction. We report here the first example of carotenoids found exclusively in the ovaries, the eggs, and the hemolymph, but not in the carcass of a female, reproductively active crustacean, i.e. the brine shrimp Artemia. These pigments are virtually absent in males and in immature animals and disappear very rapidly in growing nauplii following hatching of encysted embryos. Within the cysts, they are preferably localized in the yolk platelets. We have identified them as mono-cis- canthaxanthins on the basis of their mass and absorption spectra and by comparison with synthetic components. Carotenoids with the unusual cis-configuration have never been isolated from animals, nor are there reports on the occurrence of carotenoid pigments at specific sites. Our findings may thus provide a clue to a precise function for carotenoids in Artemia and, possibly, related Crustacea.

Animals↗
PubMed1984

Physicochemical studies on bovine eye lens proteins. II. Comparative physical study of the low-molecular-weight alpha-crystallins from calf lens cortical and nuclear fiber cells.

The alpha L of cortical and nuclear fiber cells have been studied using hydrodynamical and physicochemical techniques. From the sedimentation and the diffusion coefficients in identical conditions, it can be concluded that alpha L,N is appreciably larger than alpha L,C but both have a similar structure in solution: a spherical particle with a high hydration. The alpha L,N not only contains several degraded alpha A- and alpha B-peptides but also a typical pattern of beta-peptides. The fluorescence spectrum indicates a shift of the hydrophobic tryptophan residues from a hydrophobic environment in alpha L,C to a more solvent-exposed and polar neighbourhood for alpha L,N. Also solubility studies on alpha L,C and alpha L,N in different solvent conditions and temperatures, indicate more apolar interactions between the peptides of the nuclear alpha L, than its cortical counterpart. The more hydrophobic interaction pattern of the peptides in alpha L,N can also be reconciled with a lower mean hydration potential, indicative of a higher hydrophobicity of the degraded alpha A-peptides.

Animals↗
PubMed1982

The structure of Artemia sp. haemoglobins-I. Isolation and characterization of oxygen binding domains obtained by limited tryptic digestion.

Limited tryptic digestion of the extracellular haemoglobins of the crustacea Artemia sp. result in series of discrete fragments which are multiples of 16,000 d. 2. These 16,000 d fragments, together with 50,000 d and 80,000 d fragments have similar amino acid composition and tryptic peptide maps as the intact globin chains. 3. The haem content of the 16,000 d fragments is the same as this of the intact pigment and they can bind oxygen in a non cooperative way. 4. These results strongly support that the 16,000 d fragments represent structural and functional units or domains from which the globin chains are built up.

Amino Acids↗
PubMed1981

Biophysical characterization of Artemia salina (L.) extracellular haemoglobins.

Sedimentation coefficients (s0 20,w) of 11.57 +/- 0.10 S and 11.52 +/- 0.09 S were assigned for Artemia salina (L.) extracellular haemoglobins II and III respectively. These values are not significantly different. The molecular weights, M0w and M0z, of the native haemoglobins as determined by the high-speed sedimentation-equilibrium method were for haemoglobin II 239 400 +/- 7200 and 240 400 +/- 2600 respectively, and for haemoglobin III 216 300 +/- 6500 and 219 300 +/- 4500 respectively. The observed increase of Mapp. with concentration suggested that association was occurring over the concentration range investigated. Exposure of haemoglobin II to either 6 M-guanidinium chloride or to low pH (pH 4) resulted in dissociation to units of approximately half the size of the native protein, with molecular weights approx. 115 000. Electron-microscopic observations indicated a molecular structure composed of two stacked lobed discs. These results strongly support the dimeric model for Artemia haemoglobins proposed by Moens & Kondo [(1978) Eur. J. Biochem. 82, 65-72].

Animals↗
PubMed1981

Preferential stimulation by aurintricarboxylic acid of DNA-dependent RNA polymerase II activity in isolated larval nuclei of Artemia salina.

Aurintricarboxylic acid was found to stimulate preferentially RNA polymerase II activity in isolated nuclei of Artemia salina larvae. Studies on the in vitro transcription of a homologous chromatin indicate that this dye induces changes in the chromatin so as to enhance its template capacity for free RNA polymerase. Both free RNA polymerases I and II are equally sensitive to this dye in the absence of chromatin template. RNA polymerase II, however, becomes highly resistant to aurintricarboxylic acid when it is actively transcribing the chromatin template, whereas RNA polymerase I remains extremely sensitive even in the transcription complex. Therefore, in isolated nuclei, a preferential stimulation of alpha-amanitin-sensitive, but not-resistant RNA synthesis by aurintricarboxylic acid can be observed.

Animals↗
PubMed1981

Stabilization of native matrix granules in isolated rat heart mitochondria.

The osmiophilic granules present in the mitochondrial matrix of rat myocardium are very sensitive to changes in the energy status of the cell and in the activity of the mitochondrial electron transport. These granules can be stabilized in isolated mitochondria by blocking the electron transport with Na2S. The behaviour of these native matrix granules is similar to that expected for Ca ++ containing entities.

Amobarbital↗
PubMed1979

Ca2+ is essential cofactor for trypanocidal activity of normal human serum.

Normal human serum has been known to exert a cytotoxic effect on Trypanosoma brucei subspecies for nearly 80 yr. But in spite of many attempts, no trypanocidal factor was found in human or baboon serum, until Rifkin demostrated a high density lipoprotein (HDL) in normal human serum with trypanocidal activity. The conclusion that this was the trypanocidal factor was supported by the report that serum from patients with Tangier disease, characterised by a severe deficiency of HDL, lacked trypanocidal activity. We report here that Ca2+ is an essential cofactor for the trypanocidal activity of normal human serum, in which alpha2 macroglobulin (alpha 2) might function as a Ca2+-carrier. We further show that D-glucose, D-fructose and D-mannose can suppress the trypanocidal action of normal human serum, whereas glycerol has the opposite effect.

Calcium↗