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Biomedical subjects

J Power

Publications and source records attributed to J Power.

At least 73 records · Page 4Linked to original sources
PubMed1983

Interaction of F1-ATPase, from ox heart mitochondria with its naturally occurring inhibitor protein. Studies using radio-iodinated inhibitor protein.

The ox heart mitochondrial inhibitor protein may be iodinated with up to 0.8 mol 125I per mol inhibitor with no loss of inhibitory activity, with no change in binding affinity to submitochondrial particles, and without alteration in the response of membrane-bound inhibitor to energisation. Tryptic peptide maps reveal a single labelled peptide, consistent with modification of the single tyrosine residue of the protein. A single type of high-affinity binding site (Kd=96 . 10 (-9)M) for the inhibitor protein has been measured in submitochondrial particles. The concentration of this site is proportional to the amount of membrane-bound F1, and there appears to be one such site per F1 molecule. The ATp hydrolytic activity of submitochondrial particles is inversely proportional to the occupancy of the high-affinity binding site for the inhibitor protein. No evidence is found for a non-inhibitory binding site on the membrane or on other mitochondrial proteins. In intact mitochondria from bovine heart, the inhibitor protein is present in an approx. 1:1 ratio with F1. Submitochondrial particles prepared by sonication of these mitochondria with MgATP contain about 0.75 mol inhibitor protein per mol F1, and show about 25% of the ATPase activity of inhibitor-free submitochondrial particles. Additional inhibitor protein can be bound to these particles to a level of 0.2 mol/mol F1, with consequent loss of ATPase activity. If MgATP is omitted from the medium, or inhibitors of ATP hydrolysis are present, the rate of combination between F1 and its inhibitor protein is very much reduced. The equilibrium level of binding is, however, unaltered. These results suggest the presence of a single, high-affinity, inhibitory binding site for inhibitor protein on membrane-bound F1. The energisation of coupled submitochondrial particles by succinate oxidation or by ATP hydrolysis results in both the dissociation of inhibitor protein into solution, and the activation of ATP hydrolysis. At least 80% of the membrane-bound F1-inhibitor complex responds to this energisation by participating in a new equilibrium between bound and free inhibitor protein. This finding suggests that a delocalised energy pool is important in promoting inhibitor protein release from F1. Dissipation of the electrochemical gradient by uncouplers, or the binding of oligomycin or efrapetin effectively blocks energised release of the inhibitor protein. Conversely, the addition of aurovertin or adenosine 5'--[beta, lambda--imido]triphosphate enhances energy-driven release. The mode of action of various inhibitors on binding and energised release of the protein inhibitor is discussed.

Adenosine Triphosphate↗
PubMed1983

The dependence of maximal flow in man on the airway gas physical properties.

The changes in maximum expiratory flow rates after washing out lung air with a helium/oxygen mixture (He/O2, 80 : 20) were measured in 24 patients with chronic irreversible airflow obstruction (FEV1 1.77 +/- SD 0.39 litres; FVC 3.62 +/- 0.59 litres), and in six normal subjects. The percentage increase in flow breathing He/O2 was variable; however, it was similar in normal subjects and in patients with airflow obstruction, and in both groups decreased at low lung volumes. Contrary to previous studies, only three patients with chronic airflow obstruction failed consistently to increase flow rates by greater than or equal to 20% when breathing He/O2 at all lung volumes measured. In six normal subjects and 12 patients with chronic airflow obstruction airway gas viscosity was increased by breathing a neon/oxygen mixture (Ne/O2, 80 : 20). The response to Ne/O2 was again variable (normal subjects delta Vmax.40 4 +/- SD 14%; patients delta Vmax.40 18 +/- 8%). Only two normal subjects and one patient with airflow obstruction consistently reduced their flow rates when breathing Ne/O2. These results indicate either that there is no difference in the distribution of airflow resistance in normal subjects and in patients with chronic airflow obstruction, or that density as well as viscosity is an important determinant of flow in very small airways. In either case, He/O2 breathing is not a good discriminator of the site of airflow obstruction.

Adult↗
PubMed1976

A comparison of the virulence of three strains of Mycoplasma gallisepticum and one strain of Mycoplasma gallinarum in chicks, turkey poults, tracheal organ cultures and embryonated fowl eggs.

The virulence of three strains of Mycoplasma gallisepticum (S6 of low broth passage, S6 of high broth passage and A514) and of one strain of M gallinarum was investigated in specific pathogen free chicks, turkey poults, chick embryo tracheal organ cultures and embryonated fowl eggs. One strain of M gallisepticum, S6, of low passage, caused high mortality in newly hatched chicks, and turkey poults, high embryo mortality, and rapid suppression of ciliary activity in tracheal organ cultures. The other strains of M gallisepticum and M gallinarum had relatively less effect. In view of its greater sensitivity, chick embryo mortality is preferable to tracheal organ culture for assessing the virulence of experimental strains of M gallisepticum.

Animals↗
PubMed1972

L-arabinose isomerase formation in a conditional mutant of gene araA of Escherichia coli B-r.

A temperature-sensitive mutant of Escherichia coli in which the synthesis of l-arabinose isomerase is blocked during growth at 42 C was found to possess the following properties. (i) The mutation occurred in the structural gene for the isomerase, gene araA. (ii) During growth at elevated temperatures the mutant accumulates a product which is a precursor to the active enzyme. (iii) The precursor produced at 42 C is slowly converted to active enzyme at 28 C in the absence of protein and ribonucleic acid synthesis. It is concluded that the mutation results in a change in the structure of isomerase which causes formation of active enzyme to be thermolabile at a step beyond the level of translation.

Arabinose↗
PubMed1965

Positive control of enzyme synthesis by gene C in the L-arabinose system.

Englesberg, Ellis (University of Pittsburgh, Pittsburgh, Pa.), Joseph Irr, Joseph Power, and Nancy Lee. Positive control of enzyme synthesis by gene C in the l-arabinose system. J. Bacteriol 90:946-957. 1965.-The l-arabinose gene complex consists of genes D, A, B, and C, linked in that order between the markers thr and leu, and an unlinked gene E. Genes D, A, B, and E are the structural genes for three inducible enzymes and permease, respectively. Gene C, with two mutant alleles, C(-) and C(c), is the regulatory gene exhibiting positive and negative control. C(-) mutants are deficient and C(c) mutants are constitutive for all three enzymes and permease. Complementation analysis, employing sexual merozygotes (A(-)C(+) x A(+)C(-)), with six different C(-) mutants, demonstrates that C(-) is recessive to C(+) (positive control). A total of 61 C(c) mutants, isolated as clones resistant to d-fucose inhibition, are linked to the leu ara region of the chromosome, and the 22 C(c) mutants that were analyzed in detail mapped within the C gene among the C(-) mutant sites. C(c) mutants produce various but coordinate levels of the two enzymes measured, and permease. Complementation analysis (A(-)C(c) x A(+)C(-), A(-)C(c) x A(+)C(+)) shows that C(c) is dominant to C(-) (positive control) and recessive to C(+) (negative control). Deletion mutants that extend into the C gene are l-arabinose permease-negative, thus supporting the positive regulatory role of the C gene. The name "activator gene" is proposed for genes of the C type to accentuate their positive role in gene expression. A working model consistent with these results is presented.

Arabinose↗