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Phosphonopeptide antibacterial agents related to alafosfalin: design, synthesis, and structure-activity relationships.

Dipeptide variants of alafosfalin (L-alanyl-L-1-aminoethylphosphonic acid) with substantial differences in potency and antibacterial spectrum in vitro and in vivo have been synthesized. Certain dipeptides with alternatives to the L-alanyl residue had broader antibacterial spectra; activity against Pseudomonas aeruginosa was included. Some compounds had better in vivo activity than alafosfalin when introduced into infected rodents orally, but for the majority of the more active phosphonodipeptides, parenteral administration was more effective. Certain oligopeptides derived from the more active phosphonodipeptides possessed good in vitro activity against an extended range of organisms; they included Haemophilus influenzae, Streptococcus faecalis, and Streptococcus pneumoniae. The in vivo activity of some of these phosphono-oligopeptides was significantly greater than that of the parent dipeptide and correlated well with the in vitro results. This indicates that phosphono-oligopeptides exert part of their in vivo action directly, in addition to that arising from smaller peptides produced by peptidase cleavage.

Alanine↗

[Psychopathology of delusional disorders of an interpretive character in the course of paroxysmal schizophrenia].

Sixty patients with paroxysmal progressive schizophrenia were observed. Three variants of paroxysms were identified, viz. acute systematized interpretative delirium states; those with a mild degree of systematization and states with a mixed (interpretative-sensual) nature of delirium formation and a tendency toward delirium systematization. The psychopathological structure of every variant of these conditions was found to correlate with the clinical picture of the disease as a whole.

Acute Disease↗

Identification and characterization of the novel FAD-binding lobe G75S mutation in cytochrome b(5) reductase: an aid to determine recessive congenital methemoglobinemia status in an infant.

NADH-cytochrome b(5) reductase deficiency results clinically in either type I or type II recessive congenital methemoglobinemia. The more severe type II form is associated with a global deficiency of cytochrome b(5) reductase and is characterized by cyanosis with neurological dysfunction. In contrast, the only symptom for type I is cyanosis. We have identified a novel G to A mutation at position 15,635 in the DIAI gene of a 4-month-old baby that results in a glycine to serine substitution at codon 75 in the cytochrome b(5) reductase protein. The G75S mutation, located in the FAD-binding lobe of cytochrome b(5) reductase, was found in association with the previously described V252M variant. The V252M mutation is present in the NADH-binding domain and associated with both types I and II recessive congenital methemoglobinemia. Since the G75S and V252M mutations represent radical changes in differing regions of cytochrome b(5) reductase, generating and characterizing these variants singly and in combination using a rat heterologous expression system would provide insight into the differences between types I and II disease at the molecular level. Although all three variants were found to retain stoichiometric levels of FAD with spectroscopic and thermodynamic properties comparable to those of native cytochrome b(5) reductase, all exhibited decreased catalytic efficiency and reduced protein stability reflecting the position of the mutations in the primary structure. The G75S variant retained only 11% of the catalytic efficiency of the wild-type enzyme. Thus, cytochrome b(5) reductase deficient patients who are heterozygous for either FAD- or NADH-binding lobe mutations can exhibit the clinically less severe type I phenotype.

Amino Acid Sequence↗

Structure-function studies of apoA-I variants: site-directed mutagenesis and natural mutations.

Five mutants of apolipoprotein A-I (apoA-I), apoA-I(Delta63-73), apoA-I(Delta140-150), apoA-I(63-73@140-150), apoA-I(R149V), and apoA-I(P143A) were compared with human plasma apoA-I for their ability to promote cholesterol and phospholipid efflux from HepG2 cells. A significantly lower capacity to promote cholesterol and phospholipid efflux was observed with lipid-free apoA-I(Delta63-73), while mutations apoA-I(Delta140-150) and apoA-I(P143A) affected phospholipid efflux only. When added as apoA-I/palmitoyloleoyl phosphatidylcholine (POPC) complex, mutations apoA-I(63-73@140-150) and apoA-I(Delta140-150) affected cholesterol efflux. None of the mutations affected alpha-helicity of the lipid-free mutants or their self-association. Five natural mutations of apoA-I, apoA-I(A95D), apoA-I (Y100H), apoA-I(E110K), apoA-I(V156E), and apoA-I (H162Q) were studied for their ability to bind lipids and promote cholesterol efflux. None of the mutations affected lipid-binding properties, cholesterol efflux, or alpha-helicity of lipid-free mutants. Two mutations affected self-association of apoA-I: apoA-I(A95D) was more prone to self-association, while apoA-I(E100H) did not self-associate. The following conclusions could be made from the combined data: i) regions 210-243 and 63-100 are the lipid-binding sites of apoA-I and are also required for the efflux of lipids to lipid-free apoA-I, suggesting that initial lipidation of apoA-I is rate limiting in efflux; ii) in addition to the lipid-binding regions, the central region is important for cholesterol efflux to lipidated apoA-I, suggesting its possible involvement in interaction with cells.

Apolipoprotein A-I↗

SV40 recombinants carrying a d(CT.GA)22 sequence show increased genomic instability.

Repetitive d(CT.GA)n sequences are commonly found in eukaryotic genomic DNA. They are frequently located in sites involved in genetic recombination or in promoter regions. To test for their possible biological function, a d(CT.GA)22 synthetic sequence was introduced into the genome of SV40, since it constitutes an appropriate model system for eukaryotic chromatin. When SV40 infects permissive cells, it proliferates in the form of a minichromosome. The simple repetitive sequence indicated above was inserted at the unique HpaII site of SV40 (at nt 346), and the genomic stability of SV40 recombinants carrying the d(CT.GA)22 sequence (SV/CT22 viruses) was analyzed. Upon serial passage through permissive CV1 cells, SV/CT22 recombinants show an increased production of defective viruses. Generation of SV/CT22 variants is likely to take place via recombination between and within viral molecules. The enhancement of the rate of recombination induced by the repetitive sequence is likely to be related to its known propensity to form triple-stranded structures. Many different variants coexist in the same viral population indicating that the mechanism by which they are produced is not unique. One variant (SV/X), showing a replicative advantage, was characterized in detail. Variant SV/X accounts for a large proportion of the total viral population. Its genomic organization corresponds to a tandem duplication of an early SV40 DNA fragment spanning from approx. nt 3200-nt 160. Variant SV/X contains a duplicated SV40 ori.

Base Sequence↗

The role of the hinge loop in domain swapping. The special case of bovine seminal ribonuclease.

Bovine seminal ribonuclease (BS-RNase) is a covalent homodimeric enzyme homologous to pancreatic ribonuclease (RNase A), endowed with a number of special biological functions. It is isolated as an equilibrium mixture of swapped (MxM) and unswapped (M=M) dimers. The interchanged N termini are hinged on the main bodies through the peptide 16-22, which changes conformation in the two isomers. At variance with other proteins, domain swapping in BS-RNase involves two dimers having a similar and highly constrained quaternary association, mainly dictated by two interchain disulfide bonds. This provides the opportunity to study the intrinsic ability to swap as a function of the hinge sequence, without additional effects arising from dissociation or quaternary structure modifications. Two variants, having Pro19 or the whole sequence of the hinge replaced by the corresponding residues of RNase A, show equilibrium and kinetic parameters of the swapping similar to those of the parent protein. In comparison, the x-ray structures of MxM indicate, within a substantial constancy of the quaternary association, a greater mobility of the hinge residues. The relative insensitivity of the swapping tendency to the substitutions in the hinge region, and in particular to the replacement of Pro19 by Ala, contrasts with the results obtained for other swapped proteins and can be rationalized in terms of the unique features of the seminal enzyme. Moreover, the results indirectly lend credit to the hypothesis that the major role of Pro19 resides in directing the assembly of the non-covalent dimer, the species produced by selective reduction of the interchain disulfides and considered responsible for the special biological functions of BS-RNase.

Animals↗

Structural analysis of an electrophoretically cryptic alcohol dehydrogenase variant from an Australian population of Drosophila melanogaster.

The existence of geographically widespread clines in genetic polymorphisms is persuasive evidence that the distribution of such genetic variance is determined by natural selection. However, when comparing clines it is important to be certain that identical structural genes are involved. We report a structural difference (proline-214 to serine) between the product of AdhF and an electrophoretically cryptic heat-stable variant isolated from an Australian natural population, ADH-FCh.D. ("fast" Chateau Douglas). The biochemical properties of this new variant must be taken into consideration when attempting to formulate a causal explanation of the maintenance of the three identified Adh alleles. Our data also show that the products of an AdhF and an AdhS allele in Drosophila melanogaster in an Australian population are identical over 70% of their amino acid sequences with their North American counterparts.

Alcohol Oxidoreductases↗

Novel haplotype description and structural background of the eventual functional significance of the barley beta-amylase gene intron III rearrangements.

To extend the knowledge on the haplotype variability of the Bmy1 gene, region of the intron III was sequenced in a set of 20 Latvian accessions and Danish variety Maja, the data were compared to the previously reported allelic variants of the structural gene. Taking into account the polymorphisms of 59 loci and the microsatellite (MS) motif, 11 Latvian varieties turned out to have haplotype similar to cultivar Adorra, 1 - to Haruna Nijo, and 8 - to the newly described Abava Bmy1 intron III haplotype. High level of polymorphisms of (TG)(m) as well as (G)(n) component of MS was revealed for all the haplotypes studied. We conclude that the MS motif rather than the MS size length polymorphism correlates with mutations in the coding region of the beta-amylase gene. Five graphical haplotype-specific intron III structures were constructed on the basis of the co-localization of the transcription factor binding sites (TFBSs), remnants of the transposable elements, and intron III polymorphic loci. Inter- and intrahaplotype variability was analyzed on the eventual functional significance of the Bmy1 intron III rearrangements. Novel data on the intron III nucleotide sequences of the Bmy1 gene were deposited in the GenBank (http://www.ncbi.nlm.nih.gov/) under accession numbers DQ316895-DQ316905.

Base Sequence↗

Characterisation of the asparagine-linked oligosaccharides from Trypanosoma brucei type-I variant surface glycoproteins.

The complete primary structures of the Asn-linked oligosaccharides from the conserved glycosylation site of the type-I variant surface glycoproteins of Trypanosoma brucei MITat 1.4 and MITat 1.6 were determined using a combination of exoglycosidase digestions, permethylation analysis, acetolysis and 1H NMR. Both variants contained almost exclusively oligomannose-type oligosaccharides, identical in structure to those of mammalian glycoproteins. The oligosaccharides ranged in size from (Man)9(GlcNAc)2 to (Man)5(GlcNAc)2. The relative abundance of each component was similar in both variants. The major components were (Man)8(GlcNAc)2 and (Man)7(GlcNAc)2 with slightly less (Man)9(GlcNAc)2 and (Man)6(GlcNAc)2 and much less (Man)5(GlcNAc)2. Both variants also contained the same structural isomers. The close similarity of the oligomannose series indicates identical processing at the conserved site in both variants.

Acetone↗

Structure determination of Cryptococcus neoformans serotype A-variant glucuronoxylomannan by 13C-n.m.r. spectroscopy.

A series of polysaccharides was derived by physical and chemical methods from an antigenic, O-acetyl-containing, glucuronoxylomannan (GXM), isolated from the growth medium of Cryptococcus neoformans (CDC B2550) serotype A-variant having composition ratios of Man:Xyl:GlcA:OAc = 10:4:3:6. 13C-N.m.r. spectra of derivatives provided new structural evidence for GXM. Treatment of GXM with Li in ethylenediamine gave a xylomannan (XM, with Man:Xyl = 5:2). Smith degradation of XM gave a mannan (M). Ultrasonic treatment of GXM gave GXM-sonicated (GXMS). Treatment of GXM with 3-(3-dimethylaminopropyl)-1-ethylcarbodiimide.HCl and then with NaBH4 gave reduced GXMS (RGXMS), or with aq. trifluoroacetic acid gave partially acid-hydrolyzed GXMS. Periodate oxidation of GXM and NaBH4 reduction of the product gave a polyalcohol-mannan (PM). Treatment of GXMS, RGXMS, and PM with NH4OH at pH 11 gave the respective O-deacetylated analogs. Comparison among the 13C-n.m.r. spectra of GXM, the various derivatives, and reference monosaccharides allowed the following conclusions: M is (1----3)-alpha-D-mannopyranan; XM consists of the M backbone with 91% of the Xyl on nonadjacent Man residues as 2-O-beta-D-Xylp substituents and with 9% as 4-O-D-Xylp substituents on other Man residues. GXM consists of the XM structure, but with non-D-xylosylated Man residues substituted with 2-O-beta-D-GlcpA substituents and with 6-O-acetyl groups distributed approximately equally on Man residues that have other substituents and those that have none. The molecular mechanics program MM2 was used to estimate the relative energies of anomeric orientations of the typical glycosidic linkage in M. The results suggest that 6'-OH----O-2 H-bonding is significant in the minimal-energy orientation of M, with phi = -36 degrees and psi = 51 degrees, and that two other glycosidic orientations may be important in the 2-O- or 6-O-substituted derivatives of M.

Cryptococcus↗

X-ray structure determination and comparison of two crystal forms of a variant (Asn115Arg) of the alkaline protease from Bacillus alcalophilus refined at 1.85 A resolution.

The X-ray structure determination, refinement and comparison of two crystal forms of a variant (Asn115Arg) of the alkaline protease from Bacillus alcalophilus is described. Under identical conditions crystals were obtained in the orthorhombic space group P2(1)2(1)2(1) (form I) and the rhombohedral space group R32 (form II). For both space groups the structures of the protease were solved by molecular replacement and refined at 1.85 A resolution. The final R-factors are 17.9% and 17.1% for form I and form II, respectively. The root-mean-square deviation between the two forms is 0.48 A and 0.86 A for main-chain and side-chain atoms, respectively. Due to differences in crystal lattice contacts and packing, the structures of the two crystal forms differ in intermolecular interaction affecting the local conformation of three flexible polypeptide sequences (Ser50-Glu55, Ser99-Gly102, Gly258-Ser259) at the surface of the protein. While the two overall structures are very similar, the differences are significantly larger than the errors inherent in the structure determination. As expected, the differences in the temperature factors in form I and II are correlated with the solvent accessibility of the corresponding amino acid residues. In form II, two symmetry-related substrate binding sites face each other, forming a tight intermolecular interaction. Some residues contributing to this intermolecular interaction are also found to be involved in the formation of the complex between subtilisin Carlsberg and the proteinaceous inhibitor eglin C. This demonstrates that the two symmetry-related molecules interact with each other at the same molecular surface area that is used for binding of substrates and inhibitors.

Bacillus↗

Charge-charge interactions are key determinants of the pK values of ionizable groups in ribonuclease Sa (pI=3.5) and a basic variant (pI=10.2).

The pK values of the titratable groups in ribonuclease Sa (RNase Sa) (pI=3.5), and a charge-reversed variant with five carboxyl to lysine substitutions, 5K RNase Sa (pI=10.2), have been determined by NMR at 20 degrees C in 0.1M NaCl. In RNase Sa, 18 pK values and in 5K, 11 pK values were measured. The carboxyl group of Asp33, which is buried and forms three intramolecular hydrogen bonds in RNase Sa, has the lowest pK (2.4), whereas Asp79, which is also buried but does not form hydrogen bonds, has the most elevated pK (7.4). These results highlight the importance of desolvation and charge-dipole interactions in perturbing pK values of buried groups. Alkaline titration revealed that the terminal amine of RNase Sa and all eight tyrosine residues have significantly increased pK values relative to model compounds.A primary objective in this study was to investigate the influence of charge-charge interactions on the pK values by comparing results from RNase Sa with those from the 5K variant. The solution structures of the two proteins are very similar as revealed by NMR and other spectroscopic data, with only small changes at the N terminus and in the alpha-helix. Consequently, the ionizable groups will have similar environments in the two variants and desolvation and charge-dipole interactions will have comparable effects on the pK values of both. Their pK differences, therefore, are expected to be chiefly due to the different charge-charge interactions. As anticipated from its higher net charge, all measured pK values in 5K RNase are lowered relative to wild-type RNase Sa, with the largest decrease being 2.2 pH units for Glu14. The pK differences (pK(Sa)-pK(5K)) calculated using a simple model based on Coulomb's Law and a dielectric constant of 45 agree well with the experimental values. This demonstrates that the pK differences between wild-type and 5K RNase Sa are mainly due to changes in the electrostatic interactions between the ionizable groups. pK values calculated using Coulomb's Law also showed a good correlation (R=0.83) with experimental values. The more complex model based on a finite-difference solution to the Poisson-Boltzmann equation, which considers desolvation and charge-dipole interactions in addition to charge-charge interactions, was also used to calculate pK values. Surprisingly, these values are more poorly correlated (R=0.65) with the values from experiment. Taken together, the results are evidence that charge-charge interactions are the chief perturbant of the pK values of ionizable groups on the protein surface, which is where the majority of the ionizable groups are positioned in proteins.

Aspartic Acid↗

An isogenic hiPSC-derived keratinocyte model reveals CXCL10/CXCL11 inflammatory dysregulation in epidermolysis bullosa simplex.

Epidermolysis bullosa simplex (EBS) is a genetic skin disorder driven by dominant pathogenic variants in KRT5 or KRT14 genes, leading to cytoskeletal fragility in basal keratinocytes and intraepidermal blistering. No curative therapies are currently available, and the link between keratin mutations and disease mechanisms remains incompletely understood. To further investigate the inflammatory component of EBS, we used a model of hiPSC-derived keratinocytes carrying dominant KRT5 variants, alongside a genetically corrected isogenic counterpart. This approach established a direct link between the KRT5 variants and keratin aggregation, impaired proliferation, and an inflammatory phenotype. The inflammatory signature was confirmed by increased expression of IL1A and IL1B, consistent with previous observations in EBS, while CXCL10 and CXCL11 emerged as newly identified dysregulated chemokines. Their consistent increase across independent cell lines, elevated secretion, and normalization in the CRISPR-corrected isogenic cells indicate that KRT5 variants trigger a keratinocyte-intrinsic CXCL10/CXCL11 inflammatory response. Pharmacological inhibition of the IFN-γ-JAK1/2-STAT1 pathway suppressed their secretion, supporting JAK inhibition as a potential therapeutic strategy to modulate EBS-associated inflammatory dysregulation. In conclusion, this study shows that beyond structural defects, KRT5 variants establish a keratinocyte-intrinsic inflammatory phenotype in which the CXCL10 and CXCL11 axis emerges as a key disease-associated signature and a promising therapeutic target.

CXCL10/CXCL11↗

Characterization of the human multidrug resistance protein containing mutations in the ATP-binding cassette signature region.

A number of mutants with single amino acid replacements were generated in the highly conserved ATP-binding cassette (ABC)-signature region (amino acids 531-543) of the N-terminal half of the human multidrug resistance (MDR1) protein. The cDNA variants were inserted into recombinant baculoviruses and the MDR1 proteins were expressed in Spodoptera frugiperda (Sf9) insect cells. The level of expression and membrane insertion of the MDR1 variants was examined by immunostaining, and MDR1 function was followed by measuring drug-stimulated ATPase activity. We found that two mutations, L531R and G534V, practically eliminated MDR1 expression; thus these amino acid replacements seem to inhibit the formation of a stable MDR1 protein structure. The MDR1 variants G534D and I541R were expressed at normal levels with normal membrane insertion, but showed a complete loss of drug-stimulated ATPase activity, while mutant R538M yielded full protein expression but with greatly decreased ATPase activity. Increasing the ATP concentration did not restore MDR1 ATPase activity in these variants. Some amino acid replacements in the ABC-signature region (K536I, K536R, I541T and R543S) affected neither the expression and membrane insertion nor the ATPase function of MDR1. We found no alteration in the drug-sensitivity of ATP cleavage in any of the MDR1 variants that had measurable ATPase activity. These observations suggest that the ABC-signature region is essential for MDR1 protein stability and function, but alterations in this region do not seem to modulate MDR1-drug interactions directly.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Structurally different Drosophila striated muscles utilize distinct variants of Z-band-associated proteins.

Monoclonal antibodies raised against four proteins from insect asynchronous flight muscle have been used to characterize the cross-reacting proteins in synchronous muscle of Drosophila melanogaster. Two proteins, alpha-actinin and Z(400/600), are found at the Z-band of every muscle examined. A larger variant of alpha-actinin is specific for the perforated Z-bands of supercontractile muscle. A third Z-band protein, Z(210), has a very limited distribution. It is found only in the asynchronous muscle and in the large cells of the jump muscle (tergal depressor of the trochanter). The absence of Z(210) from the anterior four small cells of the jump muscle demonstrates that cells within the same muscle do not have identical Z-band composition. The fourth protein, projectin, greater than 600 kDa polypeptide component of the connecting filaments in asynchronous muscle, is also detected in all synchronous muscles studied. Surprisingly, projectin is detected in the region of the thick filaments in synchronous muscles, rather than between the thick filaments and the Z-band, as in asynchronous muscles. Despite their different locations, the projectins of synchronous and asynchronous muscles are very similar, but not identical, as judged by SDS-PAGE and by peptide mapping. Projectin shows immunological cross-reactivity with twitchin, a nematode giant protein that is a component of the body wall A-band and shares similarities with vertebrate titin.

Actinin↗

[State of the art of pharmacogenetic diagnostics in drug therapy].

Individual differences in the effect and side effect of drugs are partly due to genetic factors (genetic polymorphisms). The responsible polymorphisms lie in genes encoding for drug metabolism and transport but also in direct and indirect drug targets. While genetic variants in pharmacokinetic structures exert effects on drug efficacy via the differences in drug exposure, polymorphisms in drug targets can directly affect clinical efficacy and may lead to a broad variation spectrum between inefficacy and severe side effects. However, at present, our knowledge on genetic variants in drug targets is less detailed than the knowledge on pharmacogenetic variability within drug metabolism. A goal of pharmacogenetic diagnostics implemented in clinical practice is to better predict the individual drug effects on the basis of molecular-genetic profiles. Therapy recommendations can be given as dose adjustments, in particular in the case of polymorphisms of drug metabolizing enzymes which will lead to less variable drug concentrations. At present there are few examples of the application of pharmacogenetic tests in Germany in order to improve and individualize drug therapy. The reasons for this are multifold. On the one hand it is due to the limited awareness of pharmacogenetics; on the other hand it may be due to the lack of fast and economical availability of the appropriate laboratory tests. The most important reason, however, may be that most results of pharmacogenetic research are so far not translated into therapeutically usable conclusions and therapy recommendations. Thus, testing for a genotype without concrete consequences for the drug therapy of an individual patient does not make sense. Pharmacogenetic research, thereby, stands in many cases at the threshold to clinical applicability and in many cases, for instance for the genotyping for thiopurine methyltransferase polymorphisms prior to azathioprine therapy or of dihydropyrimidine dehydrogenase polymorphisms prior to treatment with 5-fluorouracil, as well as for diagnostics of CYP2D6 before therapy with certain tricyclic antidepressants and neuroleptics, one would ask already today whether a such drug therapy is still responsible without pharmacogenetic diagnostics.

Cytochrome P-450 Enzyme System↗

Structure of the coding region and mRNA variants of the apyrase gene from pea (Pisum sativum).

Partial amino acid sequences of a 49 kDa apyrase (ATP diphosphohydrolase, EC 3.6.1.5) from the cytoskeletal fraction of etiolated pea stems were used to derive oligonucleotide DNA primers to generate a cDNA fragment of pea apyrase mRNA by RT-PCR and these primers were used to screen a pea stem cDNA library. Two almost identical cDNAs differing in just 6 nucleotides within the coding regions were found, and these cDNA sequences were used to clone genomic fragments by PCR. Two nearly identical gene fragments containing 8 exons and 7 introns were obtained. One of them (H-type) encoded the mRNA sequence described by Hsieh et al. (1996) (DDBJ/EMBL/GenBank Z32743), while the other (S-type) differed by the same 6 nucleotides as the mRNAs, suggesting that these genes may be alleles. The six nucleotide differences between these two alleles were found solely in the first exon, and these mutation sites had two types of consensus sequences. These mRNAs were found with varying lengths of 3' untranslated regions (3'-UTR). There are some similarities between the 3'-UTR of these mRNAs and those of actin and actin binding proteins in plants. The putative roles of the 3'-UTR and alternative polyadenylation sites are discussed in relation to their possible role in targeting the mRNAs to different subcellular compartments.

Actins↗