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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hemoglobin (Hb) is not a glycoprotein but can easily be glycosylated by a non-enzymatic mechanism. Based on some kinetic particularities, consisting in a faster glycosylation of the amine terminal group of the beta-chain located on the allosteric site, a hypothesis of a recognition center for specific sugars has been advanced. Affinity chromatography materials based on epichlorohydrin crosslinked amylose, agarose and dextran (Sephadex), were used. A specific interaction with the CL-amylose (alpha-1,4-glycosidic links) was found, while for Sephadex (alpha-1,6-glycosidic links), no Hb retention was observed. An affinity retention of hemoglobins (human and bovine) on agarose (a galactose containing carbohydrate) has also been established. Chromatographic studies of Hb competitive elution with several monosaccharides (glucose, fructose, galactose) and disaccharides (saccharose, cellobiose, maltose, lactose) indicated that Hb retained by affinity onto CL-amylose columns, can be eluted only with galactose and lactose; with the other tested saccharides, very poor or no desorption at all, has been observed. These new data suggest: (1) a selective recognition of a limited number of (poly)saccharidic materials; and (2) a different behavior towards various sugars, the best interaction being observed with galactose-containing sugars (lactose). These aspects fit well with the hypothesis of a hemoglobin recognition center for sugars.
J Mol Recognit
PMID:Specific hemoglobin (poly)saccharide recognition. 754 Dec 25

The crystal structure of abrin-a, a type II ribosome-inactivating protein from the seeds of Abrus precatorius, has been determined from a novel crystalline form by the molecular replacement method using the coordinates of ricin. The structure has been refined at 2.14 A to a R-factor of 18.9%. The root-mean-square deviations of bond lengths and angles from the standard values are 0.013 A and 1.82 degrees, respectively. The overall protein folding is similar to that of ricin, but there are differences in the secondary structure, mostly of the A-chain. Several parts of the molecular surface differ significantly; some of them are quite near the active site cleft, and probably influence ribosome recognition. The positions of invariant active site residues remain the same, except the position of Tyr74. Two water molecules of hydrogen-bonded active site residues have been located in the active site cleft. Both of them may be responsible for hydrolyzing the N-C glycosidic bond. The current abrin-a structure is lactose free; this is probably essential for abrin-a crystallization. The B-chain is a glycoprotein, and the positions of several sugar residues of two sugar chains linked to earlier predicted glycosylation sites were determined. One of the sugar chains is a bridge between two neighboring molecules, since one of its mannose residues is connected to the galactose binding site of the neighboring molecule. Another sugar chain covers the surface of the B-chain.
J Mol Biol 1995 Jul 14
PMID:Crystal structure of abrin-a at 2.14 A. 760 80

Of four putative intramembrane charge pairs in lactose permease, only three are conserved in the homologous sucrose permease of Escherichia coli [Bockmann, J., Heuel, H., & Lengeler, J. W. (1992) Mol. Gen. Genet. 235, 22-32]. The missing charge pair was introduced into wild-type sucrose permease by site-directed mutagenesis of Asn234 (helix VII) and Ser356 (helix XI). Individual replacement of either residue with a charged amino acid abolishes active sucrose transport with the exception of the Asn234-->Asp mutant. However, simultaneous replacement of Asn234 with Asp or Glu and Ser356 with Arg or Lys results in high activity. Thus, an acidic residue at position 234 rescues the activity of the Ser356-->Arg or Ser356-->Lys mutant, and a basic residue at position 356 rescues the activity of the Asn234-->Glu mutant. Furthermore, when expressed at a relatively low rate, the double mutant Asn234-->Asp/Ser356-->Arg is present in the membrane in a significantly greater amount than wild-type, suggesting that the charge pair improves insertion of sucrose permease into the membrane. The results indicate that helices VII and XI of sucrose permease are in close proximity and that a charge pair interaction can be established between residues 234 (helix VII) and 356 (helix XI). However, interchange of the acidic residue at position 234 with the basic residue at position 356 abolishes sucrose transport.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Helix packing in the sucrose permease of Escherichia coli: properties of engineered charge pairs between helices VII and XI. 762 6

In Enterobacteriaceae the nonphosphorylated form of IIAGlc of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) can inhibit the uptake and subsequent metabolism of glycerol and maltose by binding to, and inhibiting, glycerol kinase and the MalK protein of the maltose transport system, respectively. In this report we show that the IIAGlc-like domain of the membrane-bound IIN-acetylglucosamine (IINag) of the PTS can replace IIAGlc in a Salmonella typhimurium crr mutant strain that lacks all soluble IIAGlc. The inhibition was most severe in cells which were partially induced for the glycerol or maltose uptake systems. The Streptococcus thermophilus lactose transporter LacS, which also contains a IIAGlc-like domain, could not replace IIAGlc. Neither IINag nor LacS could replace IIAGlc in activation of adenylate cyclase.
Mol Gen Genet 1995 Jul 28
PMID:Regulation of glycerol and maltose uptake by the IIAGlc-like domain of IINag of the phosphotransferase system in Salmonella typhimurium LT2. 765 47

A model repertoire of variants of immunoglobulin kappa variable domain REIv with different folding stabilities was generated by oligonucleotide-directed randomization of position 29, a key conserved residue of hypervariable loop 1. Fused to ToxR', the membrane-anchored cytoplasmic domain of the Vibrio cholerae ToxR transcription activator, different members of the library induce different levels of transcription from the ctx promoter in Escherichia coli. Differences in transcription activation correlate positively with folding stabilities of the corresponding REIv domains. Since conformationally stabilized REIv derivatives elicit a dark red colony phenotype on EMB-lactose indicator plates, this procedure constitutes a genetic screen for immunoglobulin folding stability.
J Mol Biol 1995 Aug 25
PMID:Immunoglobulin mutant library genetically screened for folding stability exploiting bacterial signal transduction. 765 65

Surfactant protein D (SP-D) is believed to contribute to nonimmune host defense within the alveoli and distal airways of the lung. SP-D molecules can bind to specific carbohydrates on the surface of bacterial, fungal, and viral organisms and can also interact with membrane glycoconjugates expressed by alveolar macrophages. Because neutrophils (PMN) and monocytes are recruited into the airspaces in association with many types of infection or lung injury, we examined the interactions of these cells with purified natural and recombinant SP-Ds, using a modified Boyden chamber assay and checkerboard analysis. Natural or recombinant rat SP-D (approximately 10(-9) to 10(-13) M) showed dose-dependent effects on human PMN and monocyte migration with a maximal response at a SP-D concentration of 5 ng/ml (approximately 10(-11) M). The migratory response was comparable to that obtained with the optimum concentration of FMLP (10(-8) M). HL-60 cells, after induction of differentiation with DMSO, responded to SP-D with the same dose-response as neutrophils. The effects of SP-D were abrogated by the simultaneous addition of SP-D to the upper chamber or by the addition of antibodies to the carboxy-terminal lectin domain. Migration toward SP-D was markedly inhibited (< 10% of controls) by 10 mM maltose but was not significantly inhibited by to 50 mM lactose. These studies establish that SP-D can bind to specific sites on neutrophils and monocytes and strongly suggest that these interactions involve the saccharide binding domains of SP-D.
Am J Respir Cell Mol Biol 1995 Apr
PMID:Interactions of pulmonary surfactant protein D (SP-D) with human blood leukocytes. 769 20

The gene for phosphatidylinositol-specific phospholipase C (PI-PLC) of Listeria monocytogenes has been cloned and shown to be expressed in Escherichia coli cells from own as well as from the lactose gene promoter. The recombinant plasmid has been constructed on the basis of pRIT2T vector and carries the hybrid gone. 3-end of which is a fragment of protein A gene of Staphylococcus aureus. 3-end is a gene for phospholipase plcA, both in the same reading frame. The resultant construction is shown to code in Escherichia coli cells for the hybrid recombinant protein A:Pl-PLC. Purified preparation of the hybrid protein and polyclonal rabbit antiserum to it were obtained. The obtained antiserum to the hybrid protein containing phospholipase as en C-end domain has been shown to react specifically to phospholipase in Escherichia coli recombinant strain harbouring the constructed recombinant plasmid as well as the one in the culture fluid of listeria.
Mol Gen Mikrobiol Virusol
PMID:[Cloning and expression of the phosphatidylinositol-specific phospholipase C gene from Listeria monocytogenes]. 773 95

Escherichia coli cells transformed with plasmids containing ricin B-chain coding sequences are shown to express this heterologous protein in inclusion bodies. After denaturation and renaturation of the product in the presence of glutathione and lactose, the recombinant ricin B-chain is soluble, biologically active and stable. Cytotoxicity of heterodimer containing this protein and ricin A-chain is found to be only ten times lower, than that of native ricin. Recombinant B-chain alone was nontoxic to cells (ID50 > 10(-6) M). Our data suggest that ricin B-chain oligosaccharides are essential for stability preserving protein from proteolytic degradation in cells.
Mol Biol (Mosk)
PMID:[Production of biologically active recombinant ricin B-chain]. 778 43

We have used the toxic non-metabolizable glucose/mannose analogue 2-deoxyglucose to isolate a comprehensive collection of mutants of the phosphoenolpyruvate:sugar phosphotransferase system from Streptococcus salivarius. To increase the range of possible mutations, we isolated spontaneous mutants on different media containing 2-deoxyglucose and various metabolizable sugars, either lactose, melibiose, galactose or fructose. We found that the frequency at which 2-deoxyglucose-resistant mutants were isolated varied according to the growth substrate. The highest frequency was obtained with the combination galactose and 2-deoxyglucose and was 15-fold higher than the rate observed with the mixture melibiose and 2-deoxyglucose, the combination that gave the lowest frequency. By combining results from: (i) Western blot analysis of IIIMan, a specific component of the phosphoenolpyruvate:mannose phosphotransferase system in S. salivarius; (ii) rocket immunoelectrophoresis of HPr and EI, the two general energy-coupling proteins of the phosphotransferase system; and (iii) from gene sequencing, mutants could be assigned to seven classes.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Microbiol 1994 Sep
PMID:Positive selection for resistance to 2-deoxyglucose gives rise, in Streptococcus salivarius, to seven classes of pleiotropic mutants, including ptsH and ptsI missense mutants. 785 24

Glu-269, which is located on the hydrophilic face of putative helix VIII in the lactose permease of Escherichia coli, has been replaced with Asp, Gln or Cys by oligonucleotide-directed, site specific mutagenesis. Cells expressing Asp-269 permease exhibit no lactose accumulation or lactose-induced H+ translocation, but retain some ability to mediate lactose influx down a concentration gradient at high substrate concentrations. Furthermore, right-side-out membrane vesicles containing Asp-269 permease do not catalyse active lactose transport, facilitated lactose efflux or equilibrium exchange. Remarkably, however, Asp-269 permease accumulates beta, D-galactopyranosyl 1-thio-beta,D-galactopyranoside in a partially uncoupled fashion, whereas no transport of methyl-beta,D-thiogalactopyranoside, sucrose or maltose is detectable. Mutant permeases containing neutral replacements (Gln or Cys) or Glu-269 are completely devoid of activity, although the proteins are present in the membrane at concentrations comparable with wild-type or Asp-269 permease. The observations demonstrate that a carboxylate at position 269 is essential for transport activity, and Glu-269 is important for substrate binding and/or recognition.
Mol Membr Biol
PMID:Role of glutamate-269 in the lactose permease of Escherichia coli. 791 10


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