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D Promé

Publications and source records attributed to D Promé.

At least 55 records · Page 3Linked to original sources
PubMed1996

Structural determination of symbiotic nodulation factors from the broad host-range Rhizobium species NGR234.

Nod factors are secreted lipo-oligosaccharides produced by symbiotic nitrogen-fixing Rhizobium bacteria that induce nodule formation on the roots of host leguminous plants. Two biologically active fractions (NodNGRA and NodNGRB) were isolated by reversed-phase HPLC from the culture supernatant of a Nod factor overproducing strain of Rhizobium sp. NGR234. NodNGRA and NodNGRB are heterogeneous mixtures of N-acylated 2-O-methylfucosylated chitomers, in which the fucosyl residue may be either 3-sulfated (NodNGRA), or 4-O-acetylated or nonsubstituted (NodNGRB). Structurally analogous series of compounds occur with either N-vaccenic (C18:1) or N-palmitic (C16:0) substituents. The presence of 6-O-carbamoyl groups on the GlcNMe-Acyl residue occurs on some molecules, while others are di-O-carbamoylated. Detailed structural analysis of seventeen Nod factors are reported here.

Carbohydrate Sequence↗
PubMed1996

Structure of the C-terminal tail of alpha-tubulin: increase of heterogeneity from newborn to adult.

A combination of posttranslational modifications contributes to the high heterogeneity of brain tubulin in mammals. In this report, the structures of the detyrosinated carboxy-terminal peptides of alpha-tubulin from newborn and adult mouse brain were compared. The heterogeneity of these carboxy-terminal peptides was observed to increase from newborn to adult brain tubulin. The major part of this increased heterogeneity is due to the post-translational excision of Glu450, which makes alpha-tubulin nontyrosinatable (delta-2 tubulin). The structures of the polyglutamyl side chain of the bi- and triglutamylated peptides were analyzed in this work. In polyglutamylation of alpha-tubulin, the first glutamyl residue can only be amide-linked to the gamma-carboxyl group of Glu445, but the additional residues may be linked either to the gamma- or to the alpha-carboxyl groups of the preceding one. By optimized reverse-phase separations and comparison with synthetic peptides corresponding to all possible linkages for the biglutamylated (gamma 1 alpha 2, gamma 1 gamma 2) and triglutamylated (gamma 1 alpha 2 alpha 3, gamma 1 gamma 2 gamma 3, gamma 1 alpha 2 gamma 3, gamma 1 gamma 2 alpha 3, gamma 1 gamma 2 alpha 2) tubulin peptides, it was possible to conclude that the mode of linkage connecting the second and third additional glutamyl residues corresponds mostly to alpha-bond structures, for both newborn and adult mice.

Aging↗
PubMed1996

Hb Uxbridge [beta 20 (B2)Val-->Gly]: a new variant with mild increase in oxygen affinity found during a neonatal screening program.

Hb Uxbridge [beta 20(B2)Val-->Gly] was found in an English family during a neonatal hemoglobinopathy screening program. In both the child and the parent carrying this hemoglobin variant, the red cell parameters were normal. By isoelectrofocusing Hb Uxbridge appeared to have an isoelectric point slightly higher than Hb A but was silent on cellulose acetate and acid gel electrophoresis. Structural modifications affecting position beta 20(B2) have been demonstrated to be responsible for a high oxygen affinity and polycythemia in Hb Olympia (Val-->Met) and Hb Trölhattan (Val-->Glu). In the case of Hb Uxbridge, despite an alteration of the same site, the oxygen binding parameters of the patient's hemolysate showed only a mild (ca. 20%) increase in oxygen affinity.

Female↗
PubMed1996

Hb Aubenas [beta 62(B8)Glu-->Gly]: a new variant normally synthesized, affecting the same codon as in Hb E.

Hb Aubenas [beta 26(B8)Glu-->Gly] is a mildly unstable variant that was found in a French family without hematological or clinical features. The structural abnormality was determined by protein chemistry methods, including tandem mass spectrometry, and was confirmed by Apa I digestion of a polymerase chain reaction-amplified DNA fragment. Although the substitution involves the same residue as in Hb E, the new nucleotide sequence does not create an additional out-of-frame splice site. The mutated chain is therefore normally synthesized.

Adolescent↗
PubMed1995

Biosynthesis of Azorhizobium caulinodans Nod factors. Study of the activity of the NodABCS proteins by expression of the genes in Escherichia coli.

By in vitro and in vivo studies with Escherichia coli expressing different combinations of the nodABCS genes of Azorhizobium caulinodans, Nod factor intermediates were identified and their structures determined using mass spectrometry. Substrate-product relationships were studied by time course experiments, and the Nod factor biosynthetic pathway was partially resolved. E. coli strains, harboring nodA and/or nodB, did not produce Nod metabolites, whereas the strain expressing nodC produced chitooligosaccharides. Thus, the first committed step was the production of the carbohydrate backbone. Bacitracin and tunicamycin did not affect this step, suggesting that undecaprenyl pyrophosphate-linked intermediates were not involved. The second step was the deacetylation of chitooligosaccharides by NodB since the E. coli strain expressing nodBC produced chitooligosaccharides, deacetylated at the non-reducing end and since the NodC products were precursors of the NodBC products. A strain expressing nodBCS produced N-methylated oligosaccharides, whereas a strain expressing nodCS produced unmethylated oligosaccharides. Time course experiments showed that methylation occurred after deacetylation. Thus, NodS acted after NodB. The NodBCS metabolites were partially converted to lipo-chitooligosaccharides when the nodABCS genes were expressed, showing that NodA was involved in the acylation and acted after NodS.

Acyltransferases↗
PubMed1995

Hemoglobin Roanne [alpha 94(G1) Asp-->Glu]: a variant of the alpha 1 beta 2 interface with an unexpected high oxygen affinity.

In hemoglobin (Hb) Roanne, the aspartate residue alpha 94(G1) is replaced by a glutamic acid. This residue plays a key role in the structural changes affecting the alpha 1 beta 2 contact area during the deoxy- to oxy-state transition in the hemoglobin molecule. Aspartate alpha 94(G1) is involved in several contacts both in the deoxy- and oxy-structures. The most important of those is a hydrogen bond with asparagine beta 102 (G4), stabilizing the oxygenated structure. Alteration of this contact usually leads to a decrease in oxygen affinity. Hb Roanne is the first example in which an increased oxygen affinity was found as a result of a structural modification at this position. Functional data suggested that the mechanisms responsible for this altered property are a destabilisation of the T-structure and a modification of the allosteric equilibrium.

Aged↗
PubMed1995

Germline mosaicism for an alanine to valine substitution at residue beta 140 in hemoglobin Puttelange, a new variant with high oxygen affinity.

Hb Puttelange [beta 140(H18)Ala-->Val] was found as a de novo mutation in two siblings of a French family suffering from polycythemia. Both parents were phenotypically normal and exclusion of paternity has been ruled out by the study of several polymorphic markers located on different chromosomes. The structural modification of Hb Puttelange was established by reversed-phase HPLC analysis of the tryptic digest of the abnormal chain. The amino acid composition of an abnormal beta T14 peptide revealed that one of the four residues of Ala was replaced by a Val. Tandem mass spectrometry demonstrated that the substitution concerned position beta 140 (H18). This hemoglobin displays an increased oxygen affinity that is responsible for the polycythemia. De novo mutations, as demonstrated again in the case of this variant, have the highest probabilities of detection when they lead to pathological manifestations. They may result either from a somatic mutation in a very early stage of the embryological development of the propositus or may have a parental origin with occurrence of a germline mosaicism. The study of the beta-globin gene indicated that this case of Hb Puttelange probably arose from a mutation affecting a part of the germline of the father, therefore leading to a true recurrence risk.

Adult↗
PubMed1995

Interaction of 2 amino acid substitutions within the same beta chain of human hemoglobin: the examples of Hb Corbeil and Hb Villeparisis.

Only 16 hemoglobin (Hb) variants carrying 2 point mutations within the same polypeptide chain have been identified up to now. Two of those are reported in this paper. In Hb Villeparisis, the beta 77 (EF1) His-->Tyr mutation is identical to that of Hb Fukuyama while the other mutation, beta 80 (EF4) Asn-->Ser, has not yet been described. These 2 abnormalities are located almost within interacting distance. They lead to decreased oxygen affinity and, according to molecular simulations, to a remodeling of the surface of the molecule. Hb Corbeil associates 2 substitutions, that of Hb E [beta 26 (B8) Glu-->Lys], and of Hb Sherwood Forest [beta 104 (G6) Arg-->Thr], which are far from one another. The resulting properties consist only in the additive effects of both abnormalities. Hb Corbeil is, thus, a thalassemic Hb, like Hb E, and a molecule having altered oxygen binding properties, characterized by decreased heterotropic effects, similar to those of Hb Sherwood Forest. The simultaneous presence of more than 1 structural abnormality leads to a large spectrum of possible consequences on the function of the molecule, from local effects to a perturbation of intermolecular interactions. The genetic mechanism resulting in Hb with more than 1 point mutation is discussed: in some cases it is very likely that the second mutation arose on a chromosome already carrying a point mutation, in contrast a single mutational event involving a micro gene conversion has been proposed in other cases.

Allosteric Site↗
PubMed1995

Hb F-Mauritius [A gamma 23 (B5) Ala deleted]: evidence for an identical hotspot for deletions in the various beta-like genes.

Hemoglobin (Hb) F-Mauritius, a new A gamma chain variant, was identified from a dried blood spot collected from a heelprick during neonatal screening for the main hemoglobinopathies. This hemoglobin is the first gamma chain variant having a one residue deletion: it concerns alanine at position gamma 23. Hb F-Mauritius is therefore the counterpart of Hb Freiburg, an unstable variant of the beta chain in which the valine residue that occupies position beta 23 is deleted. The structural modification of Hb F-Mauritius was characterized by miniaturized protein chemistry methods, including sequence determination by mass spectrometry measurements. Hb Freiburg was used as a control in several experimental procedures. The hypothesis that a similar mechanism for deletion has occurred in Hb F-Mauritius and in Hb Freiburg is supported by the high percentage of homology observed between the beta and gamma globin genes. In addition, the first exon of the beta-globin has been recognized as a hotspot for deletion: several beta-thalassemic mutations, or abnormal Hbs, with deletions of short nucleotide sequences map in this region.

Alanine↗
PubMed1995

Structural determination of a new electrophoreticaly silent variant: hemoglobin Alzette, beta 104(G6)Arg --> Lys.

A new electrophoreticaly neutral hemoglobin variant was found by ion-exchange high-performance liquid chromatography (HPLC). The molecular mass of the beta-chain was shifted down 28 mass units. The modification was found in the beta T-11 peptide that co-elutes with beta T-14 in the tryptic HPLC profile. Collision-induced decomposition of the protonated modified peptide indicated the Arg --> Lys exchange at the C-terminus. This modifies the fragmentation pattern as charge-remote processes induced by the strong basicity of arginine were replaced by charge-induced mechanisms. The exchanged 104Arg is one of the chloride binding sites in the central cavity of Hb.

Amino Acid Sequence↗
PubMed1994

Structures of nodulation factors from the nitrogen-fixing soybean symbiont Rhizobium fredii USDA257.

We have isolated and characterized the extracellular Nod factors of Rhizobium fredii USDA257, a nitrogen-fixing symbiont of soybean [Glycine max (L.) Merr.] and several other legume species. These signals are produced upon exposure to the isoflavone genistein and consist of a series of substituted, beta 1,4-linked tri-, tetra-, and pentamers of N-acetylglucosamine. N-Vaccenic acid replaces acetate on the nonreducing residue, and the reducing residue contains alpha-linked 2-O-methylfucose on carbon 6. Small amounts of a fucose-containing tetramer also were present. The Nod factors elicit root-hair deformations on soybean and two other plants at concentrations ranging from 10(-6) to 10(-12) M.

Acetylglucosamine↗
PubMed1994

The Rhizobium meliloti regulatory nodD3 and syrM genes control the synthesis of a particular class of nodulation factors N-acylated by (omega-1)-hydroxylated fatty acids.

Rhizobia elicit the formation of nitrogen-fixing nodules on specific legume hosts. Rhizobium meliloti nodulation (nod) genes control a signal exchange between the two symbiotic partners during infection and the early steps of nodulation. The regulatory nodD1, nodD2 and nodD3 genes are involved in the specific perception of different plant and environmental signals and activate the transcription of the nod operons. Once activated, the structural nod genes specify the synthesis of diffusible lipo-oligosaccharides, the Nod factors, which signal back to the plant. R. meliloti Nod factors are sulfated chito-oligosaccharides which are mono-N-acylated by unsaturated C16 fatty acids or by a series of C18 to C26 (omega-1)-hydroxylated fatty acids. In this paper we show that the regulatory nodD3 gene and another symbiotic regulatory gene, syrM, which mediate bacterial responses to plant signals that differ from those involving nodD1 and nodD2, determine the synthesis of Nod factors with different acyl moieties. nodD3 and syrM are required for the synthesis of Nod factors N-acylated by the (omega-1)-hydroxylated fatty acids. This regulatory mechanism makes possible the qualitative adaptation of bacterial Nod signal production to plant signals in the course of the symbiotic process.

Acylation↗
PubMed1993

Hb Villaverde [beta 89 (F5) Ser-->Thr]: the structural modification of an intrasubunit contact is responsible for a high oxygen affinity.

Hb Villaverde [beta 89 (F5) Ser-->Thr], identified in a Spanish patient, is a new human hemoglobin variant, electrophoreticaly silent, responsible for a severe erythrocytosis. This abnormal hemoglobin displays a very high oxygen affinity and a markedly reduced cooperativity that is partly restored in the presence of IHP. Determination of the structural abnormality was achieved on a mixture of the normal and abnormal beta-chains. After isolation of the abnormal tryptic peptide by RP-HPLC, its sequence was determined by mass spectrometry. The structural abnormality disturbs the intrasubunit interaction between helices F and H and, thus, may weaken the C-terminal bonds of the deoxy conformation and the heme contacts of several hydrophobic residues. Hb Villaverde demonstrates that this intrasubunit contact between helices F and H is essential for the cohesion of the hemoglobin molecule.

Adult↗
PubMed1993

Structures of the glycopeptidolipid antigens of two animal pathogens: Mycobacterium senegalense and Mycobacterium porcinum.

The structures of the major glycolipid antigens of two animal pathogens Mycobacterium senegalense and Mycobacterium porcinum were elucidated by a combination of fast-atom bombardment mass spectrometry, nuclear magnetic resonance spectroscopy, chemical analyses and radiolabeling experiments. Five glycoconjugates belonging to the class of C-mycoside glycopeptidolipids were characterized in each species. They shared with those recently described in M. peregrinum the same unusual distribution of the disaccharides on the alaninol end of the molecules. Both species showed the presence of the novel sulfated glycopeptidolipid. In addition, some acetylated forms of the glycolipids were also present in the species examined. Identical seroreactivities were observed between the glycolipid antigens extracted from M. senegalense, M. porcinum and M. peregrinum and an antiserum raised against the whole lipid antigens of M. peregrinum. These data reinforce the close taxonomic relationships between the three mycobacterial species and demonstrate the antigenicity of the new variants of mycobacterial glycopeptidolipids.

Animals↗
PubMed1993

Hb Saint Nazaire (beta 103[G5]Phe-->Ile): a new example of polycythemia due to a hemoglobin variant with increased oxygen affinity.

Hb Saint Nazaire [beta 103 (G5) Phe-->Ile] was found in four apparently unrelated French families. The five patients carrying this hemoglobin have been detected because of a moderate erythrocytosis. The structural abnormality of Hb Saint Nazaire concerns the same residue as in Hb Heathrow [beta 103 (G5) Phe-->Leu). A comparative functional study between these two variants showed that the increase in oxygen affinity is much lower in Hb Saint Nazaire than in Hb Heathrow. The replacement of phenylalanine G5, which is localized within the heme pocket, by a leucine abolishes several contacts between the heme and the globin and leads to an environment of the heme having some similarities with that observed in myoglobin. In contrast, the replacement of G5 by an isoleucine is likely to introduce less structural modifications.

Adolescent↗
PubMed1993

Hb Melusine [alpha 114(GH2)Pro-->Ser]: a new neutral hemoglobin variant.

Hb Melusine [alpha 114(GH2)Pro-->Ser] was found in an Algerian patient during a systematic screening for hemoglobinopathies performed in Luxembourg. The abnormal hemoglobin was suspected when a thickening of the Hb A band was observed by isoelectrofocusing. The mutant hemoglobin was silent in all other electrophoretic methods used for presumptive diagnosis with the exception of globin electrophoresis in the presence of Triton X-100. This technique revealed an alpha chain considerably more hydrophobic than normal. The structural abnormality of Hb Melusine concerns position alpha 114(GH2) that belongs to a cluster of hydrophobic residues localized in the N-terminal half of the alpha T-12b tryptic peptide. It has been shown in the case of another variant of that position (Hb Nouakchott), that the replacement of the Pro GH2 by a Leu was responsible for a dramatic increase in the retention time of the alpha polypeptide chain during reversed phase high performance liquid chromatography, much higher than that reported for similar substitutions in other regions of the hemoglobin molecule.

Adult↗
PubMed1992

Structure of tubulin C-terminal domain obtained by subtilisin treatment. The major alpha and beta tubulin isotypes from pig brain are glutamylated.

Limited subtilisin digestion of the tubulin alpha, beta heterodimer has been used in this work to reduce the total number of tubulin isotypes from 20 for native to 9 for subtilisin-cleaved tubulin. This indicates that the major part of tubulin heterogeneity is located at the C-terminus of the molecule. The C-terminal peptides of both alpha and beta subunits of tubulin were purified by anion-exchange HPLC. Combined use of Edman degradation chemistry and mass spectrometry on the isolated peptides shows that subtilisin cleavage occurs at position Asp-438 and His-406 of alpha and Gln-433 and His-396 of beta tubulin chains. Quantitative analysis of our data show that cleavage at positions His-406 (alpha) and His-396 (beta) occurs with a low efficiency and indicates that the major isotypes of pig brain tubulin are modified by sequential attachment of 1 to 5 glutamic acid residues at positions Glu-445 or -435 of alpha and beta tubulin, respectively.

Amino Acid Sequence↗