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15 recordsLinked to original sources
PubMed1976

Control of the synthesis of alkaline phosphatase and the phosphate-binding protein in Escherichia coli.

Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunological techniques, we have compared the synthesis of the phoA protein (alkaline phosphatase) and the phoS protein (phosphate-binding protein) in response to the level of phosphate in the medium in different genetic backgrounds containing the known alkaline phosphatase control mutations. Both proteins are produced in excess phosphate media in a phoR1a- strain, whereas neither protein is produced in a phoB- strain even under derepression conditions. In four different phoR1c- strains, however, the phoA product cannot be detected in extracts of cells obtained from any growth condition, whereas the phoS product is produced in both excess and limiting phosphate media. It is not yet known if phoR1c- mutants are a special class of mutations within the phoB gene or whether they occur in a separate cistron involved in alkaline phosphatase regulation. From these results we conclude that the expression of the phoA gene is not always co-regulated with expression of the phoS gene product. We have determined that the phoS protein is a component of periplasmic protein band P4 described by Morris et al. (1974). The phoS product lacks sulfur-containing amino acids and is extractable by treatment with polymyxin sulfate. The other component of band P4 contains methionine and/or cysteine and is not extracted by polymyxin sulfate treatment. Like the phoS and phoA proteins, its synthesis is sensitive to the concentration of phosphate in the growth medium. In addition, the existence of a new class of periplasmic proteins synthesized at maximum rate in high phosphate media is demonstrated.

Alkaline Phosphatase↗
PubMed1976

The presence of phosphate-binding protein in inner mitochondrial membrane.

Phosphate-binding protein(s) was found in the inner mitochondrial membrane of calf heart by Sephadex G-200 and G-25 gel filtration. The binding activity was inhibited by N-ethylmaleimide and competed by a large amount of cold phosphate. The amount of phosphate bound to the fraction was 29 nmoles per mg of protein. Affinity chromatography with phosphate-bound Sepharose 4B confirmed the presence of phosphate-binding protein(s) in the active fraction of mitochondrial membrane fractionated by gel filtration.

Carrier Proteins↗
PubMed1977

Restoration of phosphate transport by the phosphate-binding protein in spheroplasts of Escherichia coli.

Reconstitution of phosphate transport in Escherichia coli was demonstrated. Conversion of E. coli K10 cells to spheroplasts decreased phosphate transport to about 2%. Addition of purified phosphate-binding protein at physiological levels to these spheroplasts caused a mean 14-fold increase in phosphate transport rate. Crude shock fluid fractions were also stimulatory but not if the shock fluid was obtained from mutants lacking phosphate-binding protein. The effect of the binding protein was abolished by its specific antibody. The phosphate was shown to have entered the cell, where it became esterified. Reconstitution was not possible with cold-shocked or osmotically shocked cells.

Bacterial Proteins↗
PubMed1979

Purification and properties of the sn-glycerol 3-phosphate-binding protein of Escherichia coli.

A binding protein for sn-glycerol 3-phosphate was isolated from the cell envelope of Escherichia coli by the cold osmotic shock procedure. The protein was purified to homogeneity. It has a molecular weight of 45,000 and binds sn-glycerol 3-phosphate with a KD of 0.2 microM. The protein is monomeric and has L-leucine as NH2-terminal amino acid. The intrinsic fluorescence of the protein is altered upon binding of substrate. At an excitation of 285 nm, the emission maximum at 340 nm is quenched and shifted to 330 nm. Binding of sn-glycerol 3-phosphate is reversible and no chemical alteration occurs with the substrate. The appearance of the binding protein in the periplasm is the result of a mutation that renders the cells constitutive for sn-glycerol 3-phosphate transport. Simultaneously, two other proteins appear in the periplasm. These proteins were also purified. They do not bind sn-glycerol 3-phosphate and do not cross-react with antibodies against the pure binding protein.

Binding, Competitive↗
PubMed1977

Two systems for the uptake of phosphate in Escherichia coli.

Mutants of Escherichia coli K-12 were constructed such that each possessed one single major system for phosphate transport. A comparison of these strains showed that one of the systems (PIT) was fully constitutive, required no binding protein, and operated in spheroplasts. It permitted the complete exchange of intracellular phosphate with extracellular phosphate (or arsenate) and was completely inhibited by uncouplers. The other system, PST, was repressible by phosphate concentrations above 1 mM, required the phosphate-binding protein for full activity, and did not operate in spheroplasts. It catalyzed very little exchange between internal and external phosphate and was resistant to uncouplers. The maximal velocities attained by the two systems were approximately the same, but the affinity for phosphate in the PST system was greater by two orders of magnitude. In strains in which both systems were fully operative, the initial rates of uptake was nearly additive, and the systems appeared to interact with a common intracellular phosphate pool.

Arsenates↗
PubMed2024

BRCA1 safeguards genome integrity by activating chromosome asynapsis checkpoint to eliminate recombination-defective oocytes.

In the meiotic prophase, programmed DNA double-strand breaks are repaired by meiotic recombination. Recombination-defective meiocytes are eliminated to preserve genome integrity in gametes. BRCA1 is a critical protein in somatic homologous recombination, but studies have suggested that BRCA1 is dispensable for meiotic recombination. Here we show that BRCA1 is essential for meiotic recombination. Interestingly, BRCA1 also has a function in eliminating recombination-defective oocytes. Brca1 knockout (KO) rescues the survival of Dmc1 KO oocytes far more efficiently than removing CHK2, a vital component of the DNA damage checkpoint in oocytes. Mechanistically, BRCA1 activates chromosome asynapsis checkpoint by promoting ATR activity at unsynapsed chromosome axes in Dmc1 KO oocytes. Moreover, Brca1 KO also rescues the survival of asynaptic Spo11 KO oocytes. Collectively, our study not only unveils an unappreciated role of chromosome asynapsis in eliminating recombination-defective oocytes but also reveals the dual functions of BRCA1 in safeguarding oocyte genome integrity.

Oocytes↗
PubMed1979

Parathyroid autotransplantation in renal osteodystrophy.

Severe renal osteodystrophy with metaphyseal fractures developed in two children with hypoplastic-dysplastic kidneys and chronic renal failure despite therapy with vitamin D, CaCO3, phosphate-binding agents, and protein restriction. Serum immunoreactive parathyroid hormone (iPTH) levels were elevated to 709 and 1,537 pg/mL (N = 255 +/- 92 pg/mL). Total parathyroidectomy and then autotransplantation of a small portion of parathyroids into the left brachioradialis muscle resulted in complete healing of renal osteodystrophy with the same dose of vitamin D. Serum iPTH and histological studies have demonstrated functioning parathyroid autotransplants, 19 and 20 months postoperatively in these two patients. Advantage of such a procedure over 3 3/4 parathyroidectomy is that this transplanted parathyroid tissue is easily accessible for partial removal in case of recurrence of uncontrollable hyperparathyroidism. We believe that total parathyroidectomy and autotransplantation can be successfully performed even in small children.

Child, Preschool↗
PubMed1977

Studies on adenosine 3',5'-phosphate-binding and adenosine 3',5-phosphate-dependent protein kinase activities associated with subcellular fractions of Chinese hamster ovary cells.

Both cyclic AMP-binding and cyclic AMP-dependent protein kinase activities exist in Chinese hamster ovary cell extract. Competition experiments demonstrate that the binding is specific for cyclic AMP. All cellular elements including nucleus, mitochondria, plasma membrane, microsome, ribosome and cytosol contain both activities. Binding activity is highest in the cytosol and lowest in the nucleus. Each fraction contains endogenous protein kinase activity which is insensitive to cyclic AMP activation. When histone was used as a substrate, protein kinase activity in all fractions was stimulated by cyclic AMP (with the highest in cytosol and lowest in the nucleus) and inhibited by Walsh's protein kinase inhibitor.

Adenine Nucleotides↗
PubMed1975

31P nuclear-magnetic-resonance studies of pyridoxal and pyridoxamine phosphates. Interaction with cytoplasmic aspartate transaminase.

The 31P nuclear magnetic resonance (NMR) spectrum of the phosphate in free pyridoxal or pyridoxamine phosphate reveals a resonance signal that is coupled to the methylene protons of the 5-CH2 with JHP of 6.0 +/- 0.3 Hz. Proton noise decoupling results in a single signal with a pH-dependent chemical shift with deprotonation of the phosphate resulting in a shift of the 31P resonance to lower fields. A single 31P NMR signal at a frequency corresponding to fully ionized phosphate monoesters is observed in aspartate-transaminase-bound pyridoxal or pyridoxamine phosphate. The 31P resonance in the holotransaminase is pH-independent and is unaffected by saturating concentrations of substrates or inhibitors. Only denaturation with 6 M guanidine with HCl results in changes in the 31P of the holoenzyme. It appears that the phosphate group of pyridoxal phosphate is bound to a positive pocket in the holoenzyme and remains fully ionized in the pH range of 5.6 to 9.2. The phosphate-binding properties are present even in the apoenzyme which is able to bind inorganic phosphate which then can be displaced by pyridoxal or pyridoxamine phosphate in the process of holoenzyme formation.

Animals↗
PubMed1976

Serine transhydroxymethylase from rabbit liver. Sequence of anonapeptide at the pyridoxal-5'-phosphate-binding site.

The amino acid sequence of the coenzyme-binding site of serine transhydroxymethylase from rabbit liver has been determined. After reduction with NaBH4 and aminoethylation, a first sample of enzyme was digested with thermolysin and a single phosphopyridoxyl peptide was isolated. A second sample of similarly treated enzyme was digested with chymotrypsin and three phosphopyridoxyl peptides clearly originating from a unique coenzyme-binding site were isolated. Sequence analysis of these peptides indicate the following structure: Val-Val-Thr-Thr-His(Pxy)-Thr-Leu. Sequence homologies of the active site of various pyridoxalphosphate enzymes are discussed in terms of a possible catalytic role and of evolution of this class of proteins.

Amino Acid Sequence↗