摘要:

The amino acyl sequences of eight permeases (enzymes II and enzyme II‐III pairs) of the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) have been analyzed. All systems show similar sizes, and six of these systems exhibit the same molecular weight ±2%. Several exhibit sequence homology. Characteristic NH2‐terminal and COOH‐terminal sequences were found. The NH2‐terminal leader sequences are believed to function in targeting of the permeases to the membrane, whereas the characteristic COOH‐terminal sequences are postulated to mediate interaction with the energy‐coupling protein phospho HPr. One of the systems, the one specific for mannose, exhibits distinctive characteristics. A pair of probable phosphorylation sites was detected in each of the five most similar systems, those specific for β‐glucosides, sucrose, glucose,N‐acetylglucosamine, and mannitol. One of the two equivalent phosphorylation sites (proposed phosphorylation site 1) was located approximately 80 residues from the COOH terminus of each system. The other site (proposed phosphorylation site 2) was located approximately 440 residues from the COOH termini of the glucose andN‐acetylglucosamine systems, approximately 320 residues from the COOH termini of the β‐glucoside and sucrose systems, and 381 residues from the COOH terminus of the mannitol system. Intragenic rearrangement during evolutionary history may account for the different positions of phosphorylation sites 2 in the different PTS permeases. More extensive intragenic rearrangements may have given rise to entirely different positions of phosphorylation in the glucitol, mannose, and lactose systems. A single, internal amphipathic α‐helix with characteristic features was found in each of seven of the eight enzymes II. The lactose‐specific enzyme III ofStaphylococcus aureuswas unique in possessing a COOH‐terminal amphipathic a‐helix rich in basic amino acyl residues. Possible functions for these amphipathic segments are discussed.— Saier, M. H., Jr.; Yamada, M.; Erni, B.; Suda, K.; Lengeler, J.; Ebner, R.; Argos, P.; Rak, B.; Schnetz, K.; Lee, C. A.; Stewart, G. C.; Breidt, F., Jr.; Waygood, E. B.; Peri, K. G.; Doolittle, R. F. Sugar permeases of the bacterial phosphoenolpyruvate‐dependent phosphotransferase system: sequence comparisons.FASEB J.2: 199‐208; 1988.

ISSN:0892-6638    

DOI:10.1096/fasebj.2.3.2832233

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

We have developed a versatile new approach to the simultaneous analysis of families of curves, which combines the simplicity of empirical methods with several of the advantages of mathematical modeling, including objective comparison of curves and statistical hypothesis testing. The method uses weighted smoothing cubic splines; the degree of smoothing is adjusted automatically to satisfy constraints on curve chape (monotonicity, number of inflection points). By simultaneous analysis of a family of curves, one can extract the shape common to all the curves. Up to four linear scaling parameters are used to match the shape to each curve, and to provide optimal superimposition of the several curves. By applying constraints to these scaling factors, one can test a variety of hypotheses concerning comparisons of curves (e.g., identity, parallelism, or similarity of shape of two or more curves), and thus evaluate the effects of experimental manipulation. By optimal pooling of data one can avoid the need for arbitrary selection of a typical experiment, and can detect subtle but reproducible effects that might otherwise be overlooked. This approach can facilitate the development of an appropriate model. The method has been implemented in a Turbo‐Pascal program for IBM‐PC compatible microcomputers, and in FORTRAN‐77 for the DEC‐10 mainframe, and has been utilized successfully in a wide variety of applications.—guardabasso, V.;munson, P. J.Jrodbard, D. A versatile method for simultaneous analysis of families of curves.FASEB J.2: 209‐215; 1988.

ISSN:0892-6638    

DOI:10.1096/fasebj.2.3.3350235

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Group 1 introns, first demonstrated in the nuclear large rRNA ofTetrahymena thermophilaand subsequently in many yeast, fungal mitochondrial, and chloroplast precursor RNAs, are capable of intron excision and exon ligation in vitro, although this process occurs much more rapidly in vivo. The discovery and characterization of a similar intron in the T4 phage thymidylate synthase gene (td) led to the finding of additional group 1 introns in other T4 genes and in genes of the related T2 and T6 phages. Because protein factors are not required in the splicing of group 1 introns in vitro, it has been postulated that the precursor RNA can assume a critical conformation enabling it to undergo site‐specific autocatalytic cleavage and ligation (self‐splicing). By means of site‐directed mutation, it has been shown unequivocally that several sequence elements in theTetrahymenarRNA intron are involved in the formation of base‐paired stem structures that are essential for the self‐splicing process. These sequence elements have been demonstrated in other eukaryotic group 1 introns, as well as in thetdintron. In this brief review we shall describe the biochemical and structural properties of thetdintron in relation to other newly found phage introns. The interesting implications arising from these revelations will also be discussed.— Chu, F. K.; Maley, G. F.; Maley, F. RNA splicing in the T‐even bacteriophage.FASEB J.2: 216‐223; 1988.

ISSN:0892-6638    

DOI:10.1096/fasebj.2.3.3280375

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The discovery in 1919‐1924 of vitamin D and its production in skin and foods by UV irradiation led to the elimination of rickets as a major medical problem. The identification and chemical preparation of vitamin D in the next decade provided large quantities of vitamin D to the physician for the treatment of a variety of metabolic bone diseases. Early in the 1960s, little was known about the function of vitamin D in causing mineralization of the skeleton, and hence in preventing the disease rickets in children and osteomalacia in adults. With the application of modern tools of biochemistry came the discovery that vitamin D must first be modified by 25‐hydroxylation in the liver followed by 1α‐hydroxylation in the kidney to produce the vitamin D hormone 1α,25‐dihydroxyvitamin D3[1,25‐(OH)2D3]. This process is strongly feedback‐regulated and is one of the major endocrine systems regulating plasma calcium and phosphorus concentrations. Furthermore, it is a major endocrine system regulating bone mass and state. With the chemical synthesis of l,25‐(OH)2D3and many of its analogs has come the possibility of treating a number of metabolic bone diseases not previously managed adequately, such as vitamin D‐resistant rickets, hypoparathyroidism, renal osteodystrophy, and osteoporosis. By using 1,25‐(OH)2D3, considerable work has been carried out to understand how this hormone facilitates calcium transport across the intestinal membrane. Modern work is described on the molecular mechanism of action of the vitamin D hormone in eliciting the cellular responses that result in mineral homeostasis. The possible use of the vitamin D analogs to bring about differentiation of myelocytic‐type leukemias and in the treatment of psoriasis has been an important new development. This paper will thus be a blend of basic science of the vitamin D system and the application of that information to the treatment of disease.—DeLuga, H. F. The vitamin D story: a collaborative effort of basic science and clinical medicine.FASEB J.2: 224‐236; 1988.

ISSN:0892-6638    

DOI:10.1096/fasebj.2.3.3280376

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The amount and activity of superoxide dismutase (SOD) (EC 1.15.1.1) were measured in red cells collected from 50 white controls, 101 black controls, 50 patients with sickle hemoglobin (SS Hb), 12 with sickle trait, and 11 with other sickling hemoglobinopathies. Red cells from normal black subjects had more SOD amount and activity than normal whites (1.77 U/mg Hb and 2.96 μg/mg Hb vs. 1.47 U/mg Hb and 2.64 μg/mg Hb, respectively) or blacks with SS Hb or other sickling hemoglobinopathies. Patients with more severe manifestations of SS Hb had lower levels of SOD activity than those with milder symptoms but had the same amount of enzyme protein. Individuals with sickle trait had amounts and activities of SOD comparable to black controls. An alteration in defense to free radical oxygen may play a role in the severity of symptoms experienced by patients with homozygous sickle cell disease.— Schacter, L.; Warth, J. A.; Gordon, E. M.; Prasad, A.; Klein, B. L. Altered amount and activity of superoxide dismutase in sickle cell anemia.FASEB J.2: 237‐243; 1988.

ISSN:0892-6638    

DOI:10.1096/fasebj.2.3.3350236

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

To determine whether a defect in the T cell response to adenosine exists at the level of the adenosine receptor in systemic lupus erythematosus (SLE) we measured the binding affinity and maximum binding of T cell membranes from both normal and SLE T cells by utilizing radiolabeled adenosine ligands. Normal T lymphocyte membranes possess a single class of [3H]5‐N‐ethylcarboxamide adenosine binding sites with aKdof 0.61 μM, aBmaxof 23.5 pmol/mg protein, and a Hill coefficient of 0.98, which indicates the presence of noncooperative sites. In contrast, T cell membranes do not bind significant amounts of either [3H]cyclohexyladenosine or [3H]phenylisopropyladeno‐sine. These data indicate that T lymphocyte membranes have only A2, and notA1, adenosine receptors. Similarly, T cells from both active and inactive SLE subjects also express only A2receptors with aKdof 0.93 μM, aBmaxof 20.4 pmol/mg protein, and a Hill coefficient of 0.85, which is consistent with the presence of noncooperative sites. There is no difference in the on‐rate, affinity, or density of T cell A2receptors from active SLE patients, inactive SLE patients, or healthy controls. We conclude that T lymphocytes from both healthy and SLE subjects express A2, but not A1, receptors. Thus, the inability of SLE T cells to respond to adenosine does not reflect a decreased density of A2(stimulatory) receptors, diminished A2receptor binding, or an increased affinity or number of A1(inhibitory) adenosine receptors. These observations support the conclusion that the defect in the T cell cAMP‐dependent pathway may occur at a point distal to the adenosine receptor.—Schultz, L. A.; Kammer, G. M.; Rudolph, S. A. Characterization of the human T lymphocyte adenosine receptor: comparison of normal and systemic lupus erythematosus cells.FASEB J.2: 244‐250; 1988.

ISSN:0892-6638    

DOI:10.1096/fasebj.2.3.3258258

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Epidemiological data suggest that transmission of human immunodeficiency virus (HIV) occurs primarily by transference of virally infected cells. However, the efficiency of lytic productive infection induced by HIV after transmission of cell‐associated virus vs. free virus is difficult to assess. The present studies compare the extent of depletion of CD4+(helper/inducer) T cells after mixing uninfected cells with either free HIV or irradiated HIV‐infected allogeneic or autologous cells in vitro. Rapid CD4+cellular depletion occurred only in cultures containing allogeneic infected cells or after addition of a nonspecific T cell activation signal to cultures with autologous infected cells. These in vitro observations strongly support the epidemiological implication that interactions between infected and uninfected cells are the most efficient means of transmission and HIV‐induced cytopathology in vivo. They also provide direct support for the concept that immunological stimulation by foreign cells infected with HIV dramatically increases the likelihood of transmission. These in vitro observations suggest a model for the acquisition of HIV in vivo and the role of cellular activation in dissemination of the virus to uninfected cells in an infected individual.—Lewis, D. E.; Yoffe, B.; Bosworth, C. G.; Hollinger, F. B.; Rich, R. R. Human immunodeficiency virus‐induced pathology favored by cellular transmission and activation.FASEB J, 2: 251‐255; 1988.

ISSN:0892-6638    

DOI:10.1096/fasebj.2.3.2965047

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Isolated hamster hearts were perfused with 2% ethanol for 30 min and then reequilibrated with control medium. One group of hamsters was pretreated with verapamil. Another group received diltiazem. Myocardial verapamil levels were 9.5 ± 0.7 mg/g dry wt; diltiazem levels were 22 ± 7 mg/g dry wt. Energy metabolites were assessed by using31P NMR standardized with high‐pressure liquid chromatography of freeze‐clamped tissue. Intracellular calcium was measured by atomic absorption spectrophotometry, marking the extracellular space with K(CoEDTA). After 30 min of perfusion, untreated hamster hearts showed a 74% decrease in developed pressure, a marked increase in end‐diastolic pressure, a decrease of ATP from 9.8 to 8.8 mmol, and an increase of Pifrom 6.7 to 9.8 mmol, but no change of phosphocreatine (PCr) or intracellular pH (pHi). Verapamil pretreatment partially prevented cardiac depression during alcohol perfusion. Whereas diltiazem had no protective effect. After reequilibration, developed pressure and oxygen consumption significantly exceeded control values. ATP decreased to 8 mmol; pHi, PCr, and Pishowed no significant change. Verapamil‐pretreated hearts showed better performance than untreated hearts without change in PCr and Pi, whereas ATP dropped slightly to 8.7 mmol. Thus, functional cardiac depression resulting from acute alcohol exposure is reversible. Increased intracellular calcium levels during alcohol exposure normalized after the removal of alcohol. There was no major change in high‐energy phosphates during alcohol exposure or after the removal of alcohol. Verapamil protects the heart from functional depression during alcohol exposure without affecting energy resources.— Auffermann, W.; Wu, S.; Parmley, W. W.; Higgins, C. B.; Sievers, R.; Wikman‐Coffelt, J. Reversibility of acute alcohol cardiac depression:31P NMR in hamsters.FASEB J.2: 256‐263; 1988.

ISSN:0892-6638    

DOI:10.1096/fasebj.2.3.3350237

出版商:Wiley    

年代:1988

数据来源: WILEY