The gene cluster for human U2 RNA is located on chromosome 17q21

The gene cluster for human U2 RNA has been mapped to chromosome 17q21 by in situ hybridization and hybridization analysis of DNA from mouse/human somatic cell hybrids.     

A continent of plant defense peptide diversity: cyclotides in Australian Hybanthus (Violaceae)

Cyclotides are plant-derived miniproteins that have the unusual features of a head-to-tail cyclized peptide backbone and a knotted arrangement of disulfide bonds. It had been postulated that they might be an especially large family of host defense agents, but this had not yet been tested by field data on cyclotide variation in wild plant populations. In this study, we sampled Australian Hybanthus (Violaceae) to gain an insight into the level of variation within populations, within species, and between species. A wealth of cyclotide diversity was discovered: at least 246 new cyclotides are present in the 11 species sampled, and 26 novel sequences were characterized. A new approach to the discovery of cyclotide sequences was developed based on the identification of a conserved sequence within a signal sequence in cyclotide precursors. The number of cyclotides in the Violaceae is now estimated to be >9000. Cyclotide physicochemical profiles were shown to be a useful taxonomic feature that reflected species and their morphological relationships. The novel sequences provided substantial insight into the tolerance of the cystine knot framework in cyclotides to amino acid substitutions and will facilitate protein engineering applications of this framework.     

Biosynthesis of the marine antibiotic pentabromopseudilin. 2. The pyrrole ring

The biosynthesis of the potent marine antibiotic, pentabromopseudilin (1), was investigated. Feeding studies with Alteromonas luteoviolaceus were performed on a defined medium. D,L-[5-(13)C]proline was incorporated symmetrically, demonstrating that the pyrrole ring of pentabromopseudilin is derived from proline.     

A tyrosine kinase and its activator control the activity of the CtsR heat shock repressor in B. subtilis

The soil bacterium Bacillus subtilis possesses a fine-tuned and complex heat stress response system. The repressor CtsR, whose activity is regulated by its modulators McsA and McsB, controls the expression of the cellular protein quality control genes clpC, clpE and clpP. Here, we show that the interaction of McsA and McsB with CtsR results in the formation of a ternary complex that not only prevents the binding of CtsR to its target DNA, but also results in a subsequent phosphorylation of McsB, McsA and CtsR. We further demonstrate that McsB is a tyrosine kinase that needs McsA to become activated. ClpC inhibits the kinase activity of McsB, indicating a direct role in initiating CtsR-controlled heat shock response. Interestingly, the kinase domain of McsB is homologous to guanidino phosphotransferase domains originating from eukaryotic arginine and creatine kinases. Mutational analysis of key residues of the guanidino kinase domain demonstrated that McsB utilizes this domain to catalyze the tyrosine phosphorylation. McsB represents therefore a new kind of tyrosine kinase, driven by a guanidino phosphotransferase domain.     

A novel surgical procedure for bridging of massive bone defects

BACKGROUND: Bony defects arising from tumor resection or debridement after infection, non-union or trauma present a challenging problem to orthopedic surgeons, as well as patients due to compliance issues. Current treatment options are time intensive, require more than one operation and are associated with high rate of complications. For this reason, we developed a new surgical procedure to bridge a massive long bone defect. METHODS: To bridge the gap, an in situ periosteal sleeve is elevated circumferentially off of healthy diaphyseal bone adjacent to the bone defect. Then, the adjacent bone is osteotomized and the transport segment is moved along an intramedullary nail, out of the periosteal sleeve and into the original diaphyseal defect, where it is docked. Vascularity is maintained through retention of the soft tissue attachments to the in situ periosteal sleeve. In addition, periosteal osteogenesis can be augmented through utilization of cancellous bone graft or in situ cortical bone adherent to the periosteal sleeve. RESULTS: The proposed procedure is novel in that it exploits the osteogenic potential of the periosteum by replacing the defect arising from resection of tissue out of a pathological area with a defect in a healthy area of tissue, through transport of the adjacent bone segment. Furthermore, the proposed procedure has several advantages over the current standard of care including ease of implementation, rapid patient mobilization, and no need for specialized implants (intramedullary nails are standard inventory for surgical oncology and trauma departments) or costly orthobiologics. CONCLUSIONS: The proposed procedure offers a viable and potentially preferable alternative to the current standard treatment modalities, particularly in areas of the world where few surgeons are trained for procedures such as distraction osteogenesis (e.g. the Ilizarov procedure) as well as areas of the world where surgeons have little access to expensive, complex devices and orthobiologics.     

Processing of leaf matter by lake-dwelling shredders at low oxygen concentrations

Organic sediments in freshwaters are regularly subject to low concentrations of oxygen. The ability of detritivores to sustain their feeding in such conditions should therefore be of importance for the decomposition process. In the present study, aquaria were used to determine processing rates of five lake-dwelling shredders at three different oxygen concentrations; normoxic (9 mg O₂ l^–1) and two levels of hypoxia (1 and 2 mg O₂ l^–1). Discs of alder leaves (Alnus glutinosa (L.)) were used as food. Four species of caddisfly larvae (Trichoptera Limnephilidae) and the isopod, Asellus aquaticus (L.) were compared in the experiments. Significant differences in processing rates per g animal biomass were found both at normoxia and 2 mg oxygen l^–1. At l mg O₂ l^–1 none of the invertebrates fed on leaf discs. The caddisfly larvae Halesus radiatus (Curtis), being one of the two most efficient shredders at normoxia, did not feed at 2 mg oxygen l^–1. The other species fed at rates 15–50 of that at normoxia. The least efficient shredder at normoxia, A. aquaticus was similar to two of the trichopterans at 2 mg O₂ l^–1. This study shows that the importance of specific shredder species may shift in case of hypoxia. Species-specific traits regarding oxygen sensitivity may also be influential for distribution patterns of shredder species both within and between lakes.     

A comparative reactivity study of microperoxidases based on hemin, mesohemin and deuterohemin

Three microperoxidases--hemin-6(7)-gly-gly-his methyl ester (HGGH), mesohemin-6(7)-gly-gly-his methyl ester (MGGH) and deuterohemin-6(7)-gly-gly-his methyl ester (DGGH)--have been prepared as models for heme-containing peroxidases by condensation of glycyl-glycyl-L-histidine methyl ester with the propionic side chains of hemin, mesohemin and deuterohemin, respectively. The three microperoxidases differ in two substituents, R, of the protoporphyrin IX framework (HGGH: R=vinyl, MGGH: R=ethyl, DGGH: R=H). X-band and high field EPR spectra show that the microperoxidases exhibit spectroscopic properties similar to those of metmyoglobin, i.e. a high spin ferric S=5/2 signal at g(perpendicular)=6 and g parallel)=2 and an estimated D value of 7.5+/-1cm(-1). The catalytic activities of the microperoxidases towards K4[Fe(CN)6], L-tyrosine methyl ester and 2,2'-azino(bis(3-ethylbenzothiazoline-6-sulfonic acid)) (ABTS) have been investigated. It was found that all three microperoxidases exhibit peroxidase activity and that the reactions follow the generally accepted peroxidase reaction scheme [Biochem. J. 145 (1975) 93-103] with the exception that the initial formation of a Compound I analogue is the rate-limiting step for the whole process. The general activity trend was found to be MGGH approximately DGGH>HGGH. For each microperoxidase, DFT calculations (B3LYP) were made on the reactions of compounds 0, I and II with H+, e- and H+ + e-, respectively, in order to probe the possible relationship between the nature of the 2- and 4-substituents of the hemin and the observed reactivity. The computational modeling indicates that the relative energy differences are very small; solvation and electrostatic effects may be factors that decide the relative activities of the microperoxidases.     

Evolution of specialization and ecological character displacement of herbivores along a gradient of plant quality

We study the combined evolutionary dynamics of herbivore specialization and ecological character displacement, taking into account foraging behavior of the herbivores, and a quality gradient of plant types. Herbivores can adapt by changing two adaptive traits: their level of specialization in feeding efficiency and their point of maximum feeding efficiency along the plant gradient. The number of herbivore phenotypes, their levels of specialization, and the amount of character displacement among them are the result of the evolutionary dynamics, which is driven by the underlying population dynamics, which in turn is driven by the underlying foraging behavior. Our analysis demonstrates broad conditions for the diversification of a herbivore population into many specialized phenotypes, for basically any foraging behavior focusing use on highest gains while also including errors. Our model predicts two characteristic phases in the adaptation of herbivore phenotypes: a fast character-displacement phase and a slow coevolutionary niche-shift phase. This two-phase pattern is expected to be of wide relevance in various consumer-resource systems. Bringing together ecological character displacement and the evolution of specialization in a single model, our study suggests that the foraging behavior of herbivorous arthropods is a key factor promoting specialist radiation.