Role of myo-inositol in the synthesis of phosphatidylglycerol and phosphatidylinositol in the lung

The addition of $\text{myo}$-inositol to lung microsomes inhibited phosphatidylglycerol synthesis up to 94% while it stimulated that of phosphatidylinositol. The inhibition was evident only when CDP-diacylglyceride availability was limiting the rate of acidic phospholipid synthesis. Excess $\text{myo}$-inositol given to rabbits for two days decreased surfactant phosphatidylglycerol from 5.3–5.7% to 0.4–0.5%, and increased that of phosphatidylinositol from 5.4–5.8% to 9.3–8.6% of total phospholipid. The composition of other surfactant phospholipids as well as those in mitochondria and microsomes were little affected. The quality of microsomally synthesized acidic phospholipids may be controlled by $\text{myo}$-inositol at the biosynthetic surface.     

Chemical characterization, synthesis and distribution of proteinase inhibitor in newborn rat epidermis

A protein solubilized in Tris-HCl/saline buffer from keratinized cells of newborn rat epidermis exhibited inhibitor activity to papain and ficin, but not to trypsin, cathepsin D and pepsin. This protein was purified from keratinized cells as well as nonkeratinized and germinative cells by means of IgG affinity chromatography. The inhibitors extracted from all cell layers were immunologically identical and had a molecular weight of approximately 12,500 +/- 500. Since amino acid analysis showed that the inhibitor contains about 35 residues of glycine per mol, [3H]glycine was used to investigate synthesis of the protein. The inhibitor from nonkeratinized and germinative cells was radioactively labeled by 2 h after injection and appeared in keratinized cells by 48 h after injection. Indirect immunofluorescence microscopy demonstrated in situ distribution of the protein in the entire epidermis, and the protein localized by the plasma membrane in granular cells and diffusely in keratinized cells was shown to be insoluble in Tris-HCl saline buffer. The results indicate that a thiol-proteinase inhibitor is synthesized in epidermal cells during keratinization and is retained as part of the cytoplasmic structure     

Primary and secondary structure of U2 snRNA

With the improved rapid sequencing techniques, the earlier sequence of U2 RNA of Novikoff hepatoma (Shibata et al, J. Biol. Chem. 250, 3909-3920, 1975) was reanalyzed and modified. The improved sequence of U2 RNA is 188 (or 189) nucleotides long and is in register with a characterized U2 RNA pseudogene (Denison et al, PNAS 78, 810-814, 1981) except for an 11 nucleotide sequence (nucleotides 147-157) which is absent from the pseudogene. From these results, a secondary structure of U2 RNA is proposed which is supported by the preferred cleavage sites with T1-RNase, RNase A and S1 nuclease. Isolated U2 RNA was cleaved by T1-RNase preferentially at positions 64 and 164, whereas U2 RNA in U2-snRNP was cleaved only at position 64, indicating that position 164 is protected in U2-snRNP. As with U1 RNA (Epstein et al, PNAS 78, 1562-1566, 1981) the 5'-end of isolated U2 RNA was not preferentially cleaved by T1-RNase.     

H-2 antigens as genetic markers: A two-dimensional gel electrophoretic study

Direct immunoprecipitation and two-dimensional (2D) gel electrophoresis have been used to identify and characterize genetic variation of theH-2K andH-2D regions. Using inbred strains of mice and alloantisera, haplotype-specific polypeptides were defined for five differentH-2 haplotypes. Specific immunoprecipitates prepared from strains of different haplotypes were applied to 2D gels in pairwise combinations to determine whether peptides specific to one haplotype can be distinguished from peptides specific to another. Those haplotype-specific peptides that migrate to unique positions on 2D gels with respect to the positions occupied by haplotype-specific peptides of another haplotype are useful as biochemical genetic markers. Cross-reactivity amongK- andD-region antigens of different haplotypes was identified on 2D gels and found to correlate well with existing data based on serological cross-reactivity. An anti-mouse 2-microglobulin serum was found to be a useful general reagent for immunoprecipitating haplotype-specific H-2 antigens to permit their visualization on 2D gels.Abbrevations used in this paper NP-40 nonidet P-40 - 2D two-dimensional - SDS sodium dodecyl sulfate - IEF isoelectric focusing     

A K+ transport ATPase in Escherichia coli.

A K+ -stimulated ATPase in membranes of Escherichia coli has been identified as an activity of the Kdp system, and ATP-driven K+ transport system. Three characteristics support association of the ATPase with the Kdp system: (i) ATPase and Kdp transport are both repressed by growth in media containing high concentrations of K+; (ii) the ATPase and Kdp system accept only K+ as substrate, neither requires Na+ nor accepts Rb+ as a substrate; (iii) the affinity of the ATPase and that of th Kdp system for K+ is similar and is altered by mutations in the structural genes of the Kdp system. Discovery of an ATPase associated with a bacterial transport system suggests functional similarities with the ATP-driven transport systems of animal cells.     

An Inborn Error of Potassium Metabolism in the Tomato, Lycopersicon esculentum

A mutant of the tomato (Lycopersicon esculentum Mill.) was obtained through treatment of the seed with ethyl methane sulfonate. Its chief distinguishing characteristic is the requirement for an extraordinarily high K concentration in the medium (20 mm) if it is to develop without pronounced K deficiency symptoms, while the wild type grows without any such symptoms at 0.1 to 0.2 mm K. The lesion of the K-inefficient mutant does not lie in its inability to absorb and translocate K.     

Catalytic and kinetic properties of purified high-affinity cyclic AMP phosphodiesterase from dog kidney

High-affinity cyclic AMP phosphodiesterase purified to homogeneity from dog kidney was studied with respect to its stability, its catalytic and kinetic properties, and its sensitivity to pharmacological agents. The enzyme was shown to rapidly lose activity upon dilution to low protein concentrations in aqueous media, but this activity loss was largely prevented by the presence of bovine serum albumin or ethylene glycol. Similarly, maximum activity required bovine serum albumin to be present during incubation for activity analysis. Enzyme activity required a divalent cation; Mg²⁺, Mn²⁺, and Co²⁺ each supported activity, but highest activity was obtained with Mg². The temperature optimum ranged from 30 to 45 °C and depended on substrate concentration; the E_a = 10,600 cal/mol. The pH optimum of the enzyme was broad, with a maximum from pH 8.0 to 9.5. The enzyme exhibits linear Michaelis-Menton kinetics for hydrolysis of cyclic AMP at all substrate concentrations tested and for hydrolysis of cyclic GMP at > 20 μm. The K_m for cyclic AMP hydrolysis was 2 μm, and that for cyclic GMP hydrolysis was 312 μm. The K_i values for the competitive inhibition of hydrolysis of each substrate by the other were similar to their K_m values suggesting a single active site. Cyclic AMP hydrolysis was weakly inhibited by cyclic GMP, cyclic IMP, adenine, and adenosine, but was not inhibited by the mono-, di, or trinucleotides of adenosine, guanosine, or inosine. Activity was competitively inhibited with K_i values in the micromolar range by drugs representative of methylxanthines, isoquinolines, pyrazolopyridines, imidazolidinones, triazolopyrimidines, pyridylethylenediamines, phenothiazines, and calcium antagonists. The results are discussed with reference to the similarities and differences between high- and low-affinity phosphodiesterase forms.