Autophosphorylation and ADP regulate the Ca2+-dependent interaction of recoverin with rhodopsin kinase

Recoverin is a 23 kDa myristoylated Ca2+-binding protein that inhibits rhodopsin kinase. We have used surface plasmon resonance to investigate the influences of Ca2+, myristoylation, and adenine nucleotides on the recoverin-rhodopsin kinase interaction. Our analyses confirmed that Ca2+ is required for recoverin to bind RK. Myristoylation had little effect on the affinity of recoverin for the kinase, but it raised the K0.5 for Ca2+ from 150 nM for nonacylated recoverin to 400 nM for myristoylated recoverin. Finally, our studies also revealed two separate and previously unreported effects of adenine nucleotides on the recoverin-rhodopsin kinase binding. The interaction is weakened by autophosphorylation of the kinase, and it is strengthened by the presence of ADP.     

Role of divergence in evolution of group B3 Pseudomonas aeruginosa transposable phage evolution

OBJECTIVE: This study aimed to define the incidence and rate of tumor growth of acoustic neuromas (ANs) in patients who have undergone radiologic surveillance. DATA SOURCES: MEDLINE literature searches covering the period of January 1966-June 1997 were performed as well as a review of the bibliographies of the studies that were found. STUDY SELECTION: Criteria for inclusion of a study in this metaanalysis were: a defined group of patients diagnosed with an AN for whom radiologic surveillance was the selected strategy of management, limited inclusion of patients with neurofibromatosis type II (NF II) ANs, no recurrent ANs, data that could be extracted and pooled with other studies, and no duplication of patient populations between studies. Thirteen studies were selected. DATA EXTRACTION: Quality of the studies was determined by the design of each study and the ability to combine the data with the results of other studies. All of the studies were biased by their retrospective, nonrandomized nature. DATA SYNTHESIS: Paired t-tests (p < 0.05) and correlation coefficients were used to assess pooled data. CONCLUSIONS: A total of 571 ANs were studied, with an average patient age of 64 years. Given an average follow-up period of 3 years, 54% of patients showed evidence of radiologic growth. No reliable predictors of tumor growth have been identified. The authors suggest that radiologic surveillance may best be applied to those patients who refuse treatment, who have a tumor in the only-hearing ear, or who are medically unable to undergo treatment. Small tumor size and advanced age should not be viewed as absolute contraindications for treatment.     

Some developmental features of Escherichia coli Mu phage in Pseudomonas aeruginosa cells

In order to determine the replication-transposition (RT) efficiency of Escherichia coli phage Mu in Pseudomonas aeruginosa cells, the change of Mu DNA copy number after transfer of P. aeruginosa (RP4::Mu) from 42 (the condition of RP4::Mu plasmid stability and low phage production level in P. aeruginosa) to 30 degrees C (the condition of RP4::Mu plasmid instability and higher phage production level in P. aeruginosa) was analysed. It was shown that the temperature shift causes no increase in Mu DNA copy number, although free phage DNA is revealed after transfer of the cells at 30 degrees C. Considering that the studied cells contained also a linear RP4 DNA and the free Mu DNA hybridized with the RP4 DNA, we proposed that the mature Mu DNA arises as a result of Mu genome packaging from the original plasmid. So, the Mu genome RT is uneffective in P. aeruginosa and all of the phage particles released from P. aeruginosa (RP4::Mu) cells contain Mu DNA apparently originated from the DNA of hybrid plasmid RP4::Mu. Moreover, these results suggest that the Mu DNA packaging is not effective in P. aeruginosa (taking into account that the P. aeruginosa (RP4::Mu) cells release about 10(-2) p.f.u./cell and that originally the copy number of RP4::Mu > or = 1).     

Risk factors determining the outcome of a diffuse peritonitis of appendicular genesis in children

The peculiarities of pre-, intra- and early postoperative period course in 108 children, operated on for diffuse and general peritonitis of appendicitis origin, are studied. Most significant 34 prognostic factors for the disease outcome are choosed. The leading factors are the disease course duration, general condition of the patient while hospitalization, the vegetative disorders presence, the intestinal paresis degree, the biochemical inductors of stress contents, the peritoneal exudate character, the kind and composition of microorganisms in it, the character of an early postoperative period course.     

Crystalline and molecular structure of the K+-complex of meso-valinomycin, cyclo(-(D-Val-L-Hyi-L-Val-D-Hyi)3-).KAuCl4

Crystal structure of the complex of meso-valinomycin with KAuCl4 (C60H102N6O18KAuCl4) was determined using direct X-ray diffraction analysis. The conformational state of the complex is similar to that determined earlier for free meso-valinomycin. Characteristic of it is the centrosymmetric bracelet shape stabilized by six intramolecular NH...OC hydrogen bonds of 4 --> 1 type. The K+ ion is located in an inner negatively charged octahedral cavity formed by six carbonyl oxygen atoms of ester groups. The observed differences in conformational angles of the complex and free are caused by readjustment of the geometry of the ion-binding cavity to the size of the ion bound during complexation.     

The crystal and molecular structure of a valinomycin analogue cyclo[(D-Val-L-Lac-L-Ala-D-Hyi)2(D-Val-L-Lac-L-Val-D-Hyi)]. H2O(C50H82N6 O18.H2O)

The crystal and molecular structure of the valinomycin analogue, cyclo[(D-Val-L-Lac-L-Ala-D-Hyi)2(D-Val-L-Lac-L-Val-D-Hyi)] has been solved by x-ray direct methods using the "Shake and Bake" procedure. The crystals, grown from a mixture of octane/CH2Cl2, belong to space group P2(1) (Z = 4) with cell parameters a = 10.29, b = 32.08, c = 18.73 A, beta = 97.05 degrees, and contain two molecules per asymmetric unit. After anisotropic refinement the standard reliability factor was Rl = 0.058. The conformations of both independent molecules is similar to that observed for isoleucinomycin, cyclo[-(D-Ile-L-Lac-L-Ile-D-Hyi)3] [V. Z. Pletnev et al. (1980) Biopolymers, Vol. 19, pp. 1517-1534]. The structure has an asymmetric conformation stabilized by six intramolecular H bonds, five bonds being of the 4-->1 type and one bond being of the 5-->1 type. One water molecule is caged in the internal cavity of each cyclodepsipeptide. This conformation could represent an intermediate state between free and complexed forms of valinomycin.     

Mechanisms underlying the decrease in circulating angiotensin II concentration after sodium loading

1. Acute sodium loading causes a rapid decrease in the circulating concentration of angiotensin II (AngII), which is apparent from 5 min after sodium administration. This could result from an increase in AngII catabolism and/or a decrease in AngII synthesis/secretion. However, the major determinant of AngII synthesis is thought to be a change in plasma renin activity, which occurs over a longer time frame (15 min). 2. To investigate the mechanisms underlying the rapid decrease in plasma AngII engendered by sodium administration, we performed metabolic clearance studies in male New Zealand white rabbits before and after a hypertonic sodium load of 1.5 mmol/kg as 0.513 mol/L saline i.v. bolus. 3. The metabolic clearance rate of AngII increased significantly from 42.2 +/- 9.0 mL/min per kg before sodium to 110.8 +/- 33.7 mL/min per kg after sodium administration (P < 0.05). The calculated or theoretical secretion rate decreased from 1470.7 +/- 404.2 to 573.5 +/- 139.5 fmol/min per kg (P < 0.025) in response to sodium. 4. We conclude that an increase in AngII metabolism and a decrease in synthesis/secretion contribute to the reduction in circulating AngII, which occurs in the first 60-90 min after sodium loading.     

A differential response of diffuse brain injury on the concentrations of endothelin and nitric oxide in the plasma and brain regions in rats

In the present study, we hypothesized that acute diffuse brain injury (DBI) in rats would produce an increase in endothelin-1 (ET-1), a potent vasoconstrictor, and/or nitric oxide (NO), a potent vasodilator, in plasma and brain areas in rats. DBI was induced in anesthetized male Sprague-Dawley rats (350-400 g) using a 350 g weight dropped from 1 meter height impact through a device designed by Marmarou et al., 1994. Blood plasma and brain tissue (cerebral cortex, diencephalon and brain stem) samples were collected for estimation of ET-1 and NO at zero or 6 h from rats (n = 6) subjected to DBI as well as control rats (n = 6), i.e., not subjected to DBI. In a separate group of animals, cerebral blood flow (CBF) was recorded at 0, 5, 10, 15, 30, 60, 120, 240 and 360 min after induction of DBI or sham-DBI. Acute DBI produced a significant decrease in CBF at 120 min after induction of DBI. Plasma levels of ET-1 was found to be significantly increased (from 0.89 +/- 0.09 to 2.09 +/- 0.29 pg ml-1), at 6 h following DBI. DBI produced a significant decrease in the levels of ET-1 in diencephalon (from 70.97 +/- 9.47 to 57.64 +/- 2.65 pg g-1). In contrast to ET-1, DBI produced a significant increase in the concentrations of NO in the diencephalon, cerebral cortex and brain stem at 6 h post DBI. It appears that DBI-induced increase in the levels of NO in brain regions which might be down regulating the synthesis of ET-1 in diencephalon. It is concluded that ET and NO homeostatic mechanisms may play a role in the regional and vascular responses associated with acute DBI.     

Characterization of a Goalpha mutant that binds xanthine nucleotides

Several GTP binding proteins, including EF-Tu, Ypt1, rab-5, and FtsY, and adenylosuccinate synthetase have been reported to bind xanthine nucleotides when the conserved aspartate residue in the NKXD motif was changed to asparagine. However, the corresponding single Goalpha mutant protein (D273N) did not bind either xanthine nucleotides or guanine nucleotides. Interestingly, the introduction of a second mutation to generate the Goalpha subunit D273N/Q205L switched nucleotide binding specificity to xanthine nucleotide. The double mutant protein GoalphaD273N/Q205L (GoalphaX) bound xanthine triphosphate, but not guanine triphosphate. Recombinant GoalphaX (GoalphaD273N/Q205L) formed heterotrimers with betagamma complexes only in the presence of xanthine diphosphate (XDP), and the binding to betagamma was inhibited by xanthine triphosphate (XTP). Furthermore, as a result of binding to XTP, the GoalphaX protein underwent a conformational change similar to that of the activated wild-type Goalpha. In transfected COS-7 cells, we demonstrate that the interaction between GoalphaX and betagamma occurred only when cell membranes were permeabilized to allow the uptake of xanthine diphosphate. This is the first example of a switch in nucleotide binding specificity from guanine to xanthine nucleotides in a heterotrimeric G protein alpha subunit.