Aldehyde dehydrogenase (ALDH) isozymes in the gray short-tailed opossum (Monodelphis domestica): Tissue and subcellular distribution and biochemical genetics of ALDH3

Polyacrylamide gel isoelectric focusing (PAGE-IEF), cellulose acetate electrophoresis, and histochemical techniques were used to examine the tissue and subcellular distribution, genetics and biochemical properties of aldehyde dehydrogenase (ALDH) isozymes in a didelphid marsupial, the gray short-tail opossum (Monodelphis domestica). At least 14 zones of activity were resolved by PAGE-IEF and divided into five isozyme groups and three ALDH classes, based upon comparisons with properties previously reported for human, baboon, rat, and mouse ALDHs. Opossum liver ALDHs were distributed among cytosol (ALDHs 1 and 5) and large granular (mitochondrial) fractions (ALDHs 2 and 5). Similarly, kidney ALDHs were distributed between the cytosol (ALDH5) and the mitochondrial fractions (ALDHs 2, 4, and 5), whereas a major isozyme (ALDH3), found in high activity in cornea, esophagus, ear pinna, tail, and stomach extracts, was localized predominantly in the cytosol fraction. Phenotypic variants of the latter enzyme were shown to be inherited in a normal Mendelian fashion, with two alleles at a single locus (ALDH3) showing codominant expression. The data provided evidence for genetic identity of corneal, ear pinna, tail, and stomach ALDH3 and supported biochemical evidence from other mammalian species that this enzyme has a dimeric subunit structure.     

The effect of ADF/cofilin and profilin on the dynamics of monomeric actin

The main goal of the work was to uncover the dynamical changes in actin induced by the binding of cofilin and profilin. The change in the structure and flexibility of the small domain and its function in the thermodynamic stability of the actin monomer were examined with fluorescence spectroscopy and differential scanning calorimetry (DSC). The structure around the C-terminus of actin is slightly affected by the presence of cofilin and profilin. Temperature dependent fluorescence resonance energy transfer measurements indicated that both actin binding proteins decreased the flexibility of the protein matrix between the subdomains 1 and 2. Time resolved anisotropy decay measurements supported the idea that cofilin and profilin changed similarly the dynamics around the fluorescently labeled Cys-374 and Lys-61 residues in subdomains 1 and 2, respectively. DSC experiments indicated that the thermodynamic stability of actin increased by cofilin and decreased in the presence of profilin. Based on the information obtained it is possible to conclude that while the small domain of actin acts uniformly in the presence of cofilin and profilin the overall stability of actin changes differently in the presence of the studied actin binding proteins. The results support the idea that the small domain of actin behaves as a rigid unit during the opening and closing of the nucleotide binding pocket in the presence of profilin and cofilin as well. The structural arrangement of the nucleotide binding cleft mainly influences the global stability of actin while the dynamics of the different segments can change autonomously.     

Synthesis and AcidBase Properties of an Imidazole-Containing Nucleotide Analog, 1-(2'-Deoxy-β-D-ribofuranosyl)imidazole 5'-Monophosphate (dImMP(2-) )

Deletion of the substituted pyrimidine ring in purine-2'-deoxynucleoside 5'-monophosphates leads to the artificial nucleotide analog dImMP(2-) . This analog can be incorporated into DNA to yield, upon addition of Ag(+) ions, a molecular wire. Here, we measured the acidity constants of H(2) (dImMP)(±) having one proton at N(3) and one at the PO$\rm{{_{3}^{2-}}}$ group by potentiometric pH titrations in aqueous solution. The micro acidity constants show that N(3) is somewhat more basic than PO$\rm{{_{3}^{2-}}}$ and, consequently, the (H??dImMP)(-) tautomer with the proton at N(3) dominates to ca. 75%. The calculated micro acidity constants are confirmed by (31) P- and (1) H-NMR chemical shifts. The assembled data allow many quantitative comparisons, e.g., the N(3)-protonated and thus positively charged imidazole residue facilitates deprotonation of the P(O)(2) (OH)(-) group by 0.3?pK units. Information on the intrinsic site basicities also allows predictions about metal-ion binding; e.g., Mg(2+) and Mn(2+) will primarily coordinate to the phosphate group, whereas Ni(2+) and Cu(2+) will preferably bind to N(3). Macrochelate formation for these metal ions is also predicted. The micro acidity constant for N(3)H(+) deprotonation in the (H???dImMP?H)(±) species (pk(a) 6.46) and the M(n+) -binding properties are of relevance for understanding the behavior of dImMP units present in DNA hairpins and metalated duplexes.     

Changes in the ratio of free NEDD8 to ubiquitin triggers NEDDylation by ubiquitin enzymes

Ubiquitin and UBL (ubiquitin-like) modifiers are small proteins that covalently modify other proteins to alter their properties or behaviours. Ubiquitin modification (ubiquitylation) targets many substrates, often leading to their proteasomal degradation. NEDD8 (neural-precursor-cell-expressed developmentally down-regulated 8) is the UBL most closely related to ubiquitin, and its best-studied role is the activation of CRLs (cullin-RING ubiquitin ligases) by its conjugation to a conserved C-terminal lysine residue on cullin proteins. The attachment of UBLs requires three UBL-specific enzymes, termed E1, E2 and E3, which are usually well insulated from parallel UBL pathways. In the present study, we report a new mode of NEDD8 conjugation (NEDDylation) whereby the UBL NEDD8 is linked to proteins by ubiquitin enzymes in vivo. We found that this atypical NEDDylation is independent of classical NEDD8 enzymes, conserved from yeast to mammals, and triggered by an increase in the NEDD8 to ubiquitin ratio. In cells, NEDD8 overexpression leads to this type of NEDDylation by increasing the concentration of NEDD8, whereas proteasome inhibition has the same effect by depleting free ubiquitin. We show that bortezomib, a proteasome inhibitor used in cancer therapy, triggers atypical NEDDylation in tissue culture, which suggests that a similar process may occur in patients receiving this treatment.     

2,5-Diketo-gluconic acid reductase from Corynebacterium glutamicum: Characterization of stability,catalytic properties and inhibition mechanism for use in vitamin C synthesis

2,5-Diketo-d-gluconic acid (2,5-DKG) reductase is an NADPH-dependent, monomeric aldo-keto reductase (AKR) which catalyzes the reduction of 2,5-DKG to 2-keto-l-gulonic acid (2-KLG) – the immediate precursor of vitamin C. The reaction catalyzed by 2,5-DKG reductase is attractive to bypass several chemical steps and produce vitamin C biocatalytically. In a screening of 22 bacterial strains, nine 2,5-DKG reductase producing bacterial strains were found. The gene of Corynebacterium glutamicum 2,5-DKG reductase was cloned and overexpressed in Escherichia coli. By batch fermentation 409 mg L^?1 of 2,5-DKG reductase with a C-terminal His₆-tag were obtained. The purified 2,5-DKG reductase was characterized in detail. The enzyme is most active in a pH range from 5.0 to 8.0 and its stability is high at temperatures below 35 °C. Catalytic constants for 2,5-DKG and NADPH were determined and a weak inhibition by the product 2-KLG was found. 2,5-DKG reductase activity is strongly inhibited by the common process ions Mg²⁺, Ca²⁺, SO₄^3? and Cl^?, which suggests that these should be avoided in the process. The inhibition mechanism for Cl^? was elucidated. It is a competitive inhibitor with respect to NADPH and a noncompetitive inhibitior with respect to 2,5-DKG.     

Substantial Metabolic Activity of Human Brown Adipose Tissue during Warm Conditions and Cold-Induced Lipolysis of Local Triglycerides

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A survey of alkaloids in the genera Harpalyce and Brongniartia (Fabaceae—Brongniartieae)

The presence of alkaloids in six species of Brongniartia and three species of Harpalyce is reported. This survey revealed remarkable qualitative differences in the alkaloid profiles of these two genera. B. discolor, B. lupinoides, B. sousae and B. intermedia showed a typical -pyridone pattern, with cytisine, anagyrine and baptifoline as major alkaloids. In leaves of the first three species ormosanine-type alkaloids occurred additionally. B. flava and B. vazquezii are devoid of -pyridones, but accumulate lupanine, hydroxylated lupanines and ester alkaloids. All three species of Harpalyce were similar in accumulating -pyridones, but H. formosa differed from H. brasiliana and H. pringlei in the presence of epilupinine. In general the alkaloid profiles of Brongniartia and Harpalyce show similarities to those of the Australian genera Hovea, Lamprolobium, Plagiocarpus and Templetonia and support therefore the actual concept of the enlarged tribe Brongniartieae.     

Structural studies of an acidic polysaccharide from the mucin secreted by Drosera capensis

The polysaccharide of the mucin secreted by the leaves of Drosera capensis is composed of l-arabinose, d-xylose, d-galactose, d-mannose, and d-glucuronic acid in the molar ratio of 3.6:1.0:4.9:8.4:8.2. For structural elucidation, methylation analysis using g.l.c. and g.l.c.-m.s. was performed on the native, the carboxyl-reduced, and the degraded polysaccharides. Partial hydrolysis, periodate oxidation, chromium trioxide oxidation, and uronic acid degradation were also performed on the native and carboxyl-reduced polysaccharides. Partial hydrolysis of the native and carboxyl-reduced polysaccharides gave various oligosaccharides that were characterized and suggest a structure containing a d-glucurono-d-mannan backbone having a repeating unit → 4)-β-d-GlcpA-(1 → 2)-α-d-Manp-(1 →. l-Arabinose and d-xylose are present as nonreducing furanosyl and pyranosyl end-groups, respectively, both attached to O-3 of d-glucuronic acid residues of the backbone. d-Galactose is present as non-reducing pyranosyl end-group linked to O-3 of d-mannose residues.     

Effects of the Introduction of Agrobacterium tumefaciens T-DNA ipt Gene in Nicotiana tabacum L. cv. Petit Havana SR1 Plant Cells

Transformation of tobacco leaf discs with the ‘cytokinin’ipt gene yielded several transgenic callus tissue lines, respectiveto the kind of ipt construction present in the A. tumefacienscointegrates. Those calli containing an active ipt gene wereable to grow hormone-autotrophically and showed an increasedendogenous cytokinin level in comparison with controls. Analysisof endogenous IAA level did not allow any quantitative correlationwith the cytokinin content. However, a minimal level of auxinseems to be necessary to obtain hormone-autotrophic growth.Exogenously supplied NAA significantly reduced the endogenouscytokinin content without modifying growth characteristics. The varying chlorophyll content in the different callus lineselicited the study of the ultrastructure of the plastids. Thecontrols contained small plastids, often filled with starchor accumulated vesicles that did not allow observation of theinternal membrane system. The ‘Pssu-ipt’ line, havinga higher cytokinin content, showed plastids with an internalmembrane system consisting of stroma and grana thylakoids, butthis structure was lost during subculture. Swollen thylakoidsappeared, the amount of starch was reduced and vesicles wereaccumulating. (Received November 15, 1990; Accepted March 4, 1991)     

Gene Order of Encephalomyocarditis Virus as Determined by Studies with Pactamycin

Previous work has shown that translation of the encephalomyocarditis (EMC) viral ribonucleic acid (RNA) generates at least three primary products, polypeptides A, F, and C. The A and C polypeptides then undergo post-translational cleavages to complete the production of the stable viral polypeptides (delta, beta, gamma, alpha, G, I, F, H, and E). In this communication we show that A, F, and C are produced in equimolar amounts giving further support to the theory that the RNA of picornaviruses has only a single site for the initiation of protein synthesis. The biosynthesis of viral proteins in EMC virus-infected HeLa cells was studied in the presence of pactamycin at concentrations which preferentially inhibit the initiation of protein synthesis. The amount of each polypeptide formed during the residual period of protein synthesis observed after the addition of pactamycin was used as a criterion for ordering the genes on the viral RNA. The results obtained indicate that the primary gene products are ordered on the EMC viral RNA 5' --> 3' A-F-C and that the stable products are ordered delta-beta-gamma-alpha-G-I-F-H-E. Moreover, the intermediate chains B and epsilon map in the capsid region, whereas the intermediate chain D maps in the E region. This order is largely consistent with previously established relationships of the viral polypeptides and thus indicates that pactamycin is a valid tool for "genetic" mapping of polycistronic RNA molecules with single initiation sites.