Genetic mapping of the ilv7434 mutation providing threonine deaminase resistance to isoleucine inhibition in Escherichia coli

Location of previously isolated ilv7434 mutation was determined by use of transductional shortening of the F'14 episome. The ilv7434 mutation causes resistance of threonine deaminase (coded for by ilvA gene) to feed-back inhibition by isoleucine. Another phenotype characteristics of the ilv7434 mutant is the ability to feed a lawn of isoleucine auxotrophs in the cross-streak test. The F'14 strain AB1206 carrying ilv7434 mutation was used as a donor for making transductionally shortened episomes in recA recipient. These shortened F'14 episomes containing variable segments of the ilv cluster were then tested for their ability to transfer ilv7434 phenotype by complementation with ilv recA recipients. The data of complementation test suggest that ilv7434 is situated between ilvD and ilvC genes. One of 20 tested shortened episomes carrying, as shown by complementation test, incomplete ilvA gene was found to transfer ilv7434 phenotype by recombination with ilvA527 recA+ recipient. These data allow to conclude that ilv7434 mutation is located within the ilvA gene.     

Divergent Dimethylarginine Dimethylaminohydrolase Isoenzyme Expression in the Central Nervous System

Cellular and Molecular Neurobiology - The endogenous methylated derivative of ʟ-arginine, Nω,Nω′-dimethyl-ʟ-arginine (asymmetric dimethylarginine, ADMA), an independent...     

Nucleotide composition and contents of CpG and CpNpG in the ITS1, ITS2 and 5.8S rRNA of the representatives of phylogenetic branches of melanthiales-liliales and melanthiales and melanthiales-asparagales (angiospermae, monocotyledones) reflects a characteristic feature of evolution

Variations of nucleotide composition and frequency of CpG and CpNpG sequences in the clusters of nuclear ribosomal genes of taxa, belonging to two phylogenetic branches of Angiospermae have been statistically analyzed. This region of eucaryotic genomes is nucleolus organizer and functions in a separate compartment of cell nucleus that can do running here processes it is enough specific. It is shown that level of evolution advance of a taxon, defined on morphological data, is in positive correlation with quantitative value of dC, CpG and CpNpG. This is found in contradiction with beliefs about the general rules of the transformation of nucleotide composition in evolution, that suggest a CpG suppression. Cryptaffinous taxa being connecting link between a well morphological outlined taxonomic group, differ to be raised in     

Comparative genomic analyses of nickel, cobalt and vitamin B12 utilization

Background

Nickel (Ni) and cobalt (Co) are trace elements required for a variety of biological processes. Ni is directly coordinated by proteins, whereas Co is mainly used as a component of vitamin B₁₂. Although a number of Ni and Co-dependent enzymes have been characterized, systematic evolutionary analyses of utilization of these metals are limited.

Results

We carried out comparative genomic analyses to examine occurrence and evolutionary dynamics of the use of Ni and Co at the level of (i) transport systems, and (ii) metalloproteomes. Our data show that both metals are widely used in bacteria and archaea. Cbi/NikMNQO is the most common prokaryotic Ni/Co transporter, while Ni-dependent urease and Ni-Fe hydrogenase, and B₁₂-dependent methionine synthase (MetH), ribonucleotide reductase and methylmalonyl-CoA mutase are the most widespread metalloproteins for Ni and Co, respectively. Occurrence of other metalloenzymes showed a mosaic distribution and a new B₁₂-dependent protein family was predicted. Deltaproteobacteria and Methanosarcina generally have larger Ni- and Co-dependent proteomes. On the other hand, utilization of these two metals is limited in eukaryotes, and very few of these organisms utilize both of them. The Ni-utilizing eukaryotes are mostly fungi (except saccharomycotina) and plants, whereas most B₁₂-utilizing organisms are animals. The NiCoT transporter family is the most widespread eukaryotic Ni transporter, and eukaryotic urease and MetH are the most common Ni- and B₁₂-dependent enzymes, respectively. Finally, investigation of environmental and other conditions and identity of organisms that show dependence on Ni or Co revealed that host-associated organisms (particularly obligate intracellular parasites and endosymbionts) have a tendency for loss of Ni/Co utilization.

Conclusion

Our data provide information on the evolutionary dynamics of Ni and Co utilization and highlight widespread use of these metals in the three domains of life, yet only a limited number of user proteins.     

Cytoplasmic dynein is involved in the retention of microtubules at the centrosome in interphase cells

Cytoplasmic dynein is known to be involved in the establishment of radial microtubule (MT) arrays. During mitosis, dynein activity is required for tethering of the MTs at the spindle poles. In interphase cells, dynein inhibitors induce loss of radial MT organization; however, the exact role of dynein in the maintenance of MT arrays is unclear. Here, we examined the effect of dynein inhibitors on MT distribution and the centrosome protein composition in cultured fibroblasts. We found that while these inhibitors induced rapid ( t _1/2 ∼ 20 min) loss of radial MT organization, the levels of key centrosomal proteins or the rates of MT nucleation did not change significantly in dynein-inhibited cells, suggesting that the loss of dynein activity does not affect the structural integrity of the centrosome or its capacity to nucleate MTs. Live observations of the centrosomal activity showed that dynein inhibition enhanced the detachment of MTs from the centrosome. We conclude that the primary role of dynein in the maintenance of a radial MT array in interphase cells consists of retention of MTs at the centrosome and hypothesize that dynein has a role in the MT retention, separate from the delivery to the centrosome of MT-anchoring proteins.     

Zn(2+)-mediated structure formation and compaction of the "natively unfolded" human prothymosin alpha

Human recombinant prothymosin alpha (ProTalpha) is known to have coil-like conformation at neutral pH; i.e., it belongs to the class of "natively unfolded" proteins. By means of circular dichroism, SAXS, and ANS fluorescence, we have investigated the effect of several divalent cations on the structure of this protein. Results of these studies are consistent with the conclusion that ProTalpha conformation is unaffected by large excess of Ca(2+), Mg(2+), Mn(2+), Cu(2+), and Ni(2+). However, Zn(2+) induces compaction and considerable rearrangement of the protein structure. This means that ProTalpha can specifically interact with Zn(2+) (K(D) approximately 10(-3) M), and such interactions induce folding of the natively unfolded protein into a compact partially folded (premolten globule-like) conformation. It is possible that these structural changes may be important for the function of this protein.     

Beta-lactam-induced bacteriolysis of amino acid-deprived Escherichia coli is dependent on phospholipid synthesis.

The penicillin tolerance of amino acid-deprived relA+ Escherichia coli is attributed to the stringent response; i.e., relaxation of the stringent response suppresses penicillin tolerance. The beta-lactam-induced lysis of amino acid-deprived bacteria resulting from relaxation of the stringent response was inhibited by cerulenin, or by glycerol deprivation in the case of a gpsA mutant (defective in the biosynthetic sn-glycerol 3-phosphate dehydrogenase). Therefore, beta-lactam-induced lysis of amino acid-deprived cells was dependent on phospholipid synthesis. The lysis process during amino acid deprivation can be experimentally dissociated into two stages designated the priming stage (during which the interaction between the beta-lactam and the penicillin-binding proteins occurs) and the beta-lactam-independent lysis induction stage. Both stages were shown to require phospholipid synthesis. It has been known for some time that the inhibition of phospholipid synthesis is among the plethora of physiological changes resulting from the stringent response. These results indicate that the inhibition of peptidoglycan synthesis and the penicillin tolerance associated with the stringent response are both secondary consequences of the inhibition of phospholipid synthesis.