Continuous gas-depletion technique for measuring O2-dissociation curves of high-affinity hemoglobins

The O2-depletion technique allows a continuous measurement of the complete O2-dissociation curve of high-affinity hemoglobins in the O2-partial pressure range of 700 to 10(-4) mm Hg. With this technique p50 values greater than or equal to 0.01 mm Hg (approximately equal to 1.3 Pa) can be determined for 3-microliter hemoglobin samples. As examples, O2-dissociation curves of sperm whale myoglobin (p50 = 0.9 mm Hg, 25 degrees C, pH 8.0) and Dicrocoelium hemoglobin (p50 = 0.06 mm Hg, 25 degrees C, pH 4.9) are demonstrated which show Hill coefficients of n = 1.0 over the complete O2-saturation range.     

Adenovirus serotype determines association and localization of the large E1B tumor antigen with cellular tumor antigen p53 in transformed cells.

The distribution and stability of the cellular tumor antigen p53 were studied in baby rat kidney cells transformed by region E1 sequences of nononcogenic adenovirus (Ad) type 5 (Ad5) or oncogenic type 12 (Ad12). In transformed cells expressing the large E1B T antigen of Ad5, p53 was associated with this T antigen. The complexed proteins were concentrated in a cytoplasmic body, which has been shown to consist of a cluster of 8-nm filaments (A. Zantema et al., Virology 142:44-58, 1985). In transformed cells expressing the E1B region of Ad12, however, no association between the viral large T antigen and p53 was detectable. In the latter case, both proteins were found almost exclusively in the nucleus. The stability of p53 in both Ad5- and Ad12-transformed cells was increased relative to that in primary cells or cells immortalized by the E1A region only. Thus, the increased stability of p53 in Ad-transformed cells is not caused by association with a viral T antigen, but it correlates with expression of E1B and with morphological transformation.     

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Assignment of proximal histidyl imidazole exchangeable proton NMR resonances to individual subunits in hemoglobins A,Boston, Iwate and Milwaukee

The proton nmr spectra of the synthetic valency hybrids, α₂(β⁺CN)₂, (α⁺CN)₂β₂ of hemoglobin A and the natural valency hybrids of the mutant hemoglobins Boston, Iwate and Milwaukee have led to the unambiguous assignment of the two proximal histidyl imidazole exchangeable proton signals at 64 and 76 ppm to individual α and β subunits, respectively. New single non-exchangeable proton resonances detected in the extreme downfield region of the spectra of Hbs Boston and Iwate are tentatively assigned to the coordinated tyrosine of the mutated α chains.     

Anoxic survival of the isolated cerebellum of the turtle Pseudemis scripta elegans

Intact turtle brain provides a useful model for the study of anoxia and potential survival strategies, since this tissue maintains transmembrane ion gradients and ATP levels during prolonged anoxia and recovers functional activity afterwards. Since isolated tissues offer experimental advantages, the present study sought to determine effects of anoxia on the isolated turtle cerebellum and to define relationships between anoxia survival and glucose supply. In normoxia, the extracellular potassium ([K+]o) activity and evoked potentials were maintained with 5 mM glucose, but 20 mM glucose was required to maintain adenosine triphosphate (ATP) levels and prevent significant increases in [K+]o during anoxia. Inhibition of glycolysis by iodoacetic acid (IAA) during anoxia provoked large increases in [K+]o at all glucose levels. These results demonstrate the usefulness of the isolated turtle cerebellum for studies of anoxic survival since this tissue can maintain ATP levels and [K+]o during prolonged anoxia with 20 mM glucose in the artificial cerebrospinal fluid medium. They also suggest the presence of a Pasteur effect at least during the transition to a hypometabolic state.     

Co-binding studies on Hb M Iwate. Allostery of a T state haemoglobin.

The mutant haemoglobin Hb M Iwate alpha 2Mmet87His leads to Tyr beta 2, is characterized by a stable T structure and a low ligand affinity. Sigmoidal CO-binding isotherms of symmetrical shape with Hill coefficients of n = 1.4 at pH 6 to n = 1.9 at pH 10 and the differences in the mean affinity (PCO(1/2)) and the affinity of the first ligand-binding beta subunit (1/L1 greater than Pco(1/2)) are the evidence for the cooperativity. The comparison of the Bohr effects of the two valency hybrid states (alpha 2Mmet beta met beta deoxy alpha 2Mmet beta 2deoxy) in the absence of and in the presence of polyphosphates leads to an indirect proof of pH-dependent subunit-subunit interaction. Inositol hexaphosphate-binding suppresses cooperativity in the pH range 5.5-8 (n = 1). Above pH 8 hte cooperativity increases to a final value of n = 1.9 at pH greater than 10, which is identical to that of stripped Hb M Iwate. The CO binding to the first binding site exhibits a Bohr effect. Polyphosphate anions have no influence on the CO binding of the first binding site. The heterotropic effects are discussed as intrachain effects (Bohr effect of the first binding site) and interchain effects (Bohr effect of Pco(1/2); influence of polyphosphates).     

STING Millennium Suite: integrated software for extensive analyses of 3d structures of proteins and their complexes

Background  

The integration of many aspects of protein/DNA structure analysis is an important requirement for software products in general area of structural bioinformatics. In fact, there are too few software packages on the internet which can be described as successful in this respect. We might say that what is still missing is publicly available, web based software for interactive analysis of the sequence/structure/function of proteins and their complexes with DNA and ligands. Some of existing software packages do have certain level of integration and do offer analysis of several structure related parameters, however not to the extent generally demanded by a user.     

Sex chromosome linkage of chicken and duck type I interferon genes: further evidence of evolutionary conservation of the Z chromosome in birds

Type I interferons (IFNs) are a family of proteins that are predominantly expressed in response to viral infection. Two serologically distinct forms of type I IFN, designated ChIFN1 and ChIFN2, have recently been recognized in the chicken. ChIFN1 is encoded by a cluster of ten or more intronless genes, whereas ChIFN2, whose primary sequence is 57% identical, is encoded by a single intronless gene. By fluorescence in situ hybridization we now demonstrate that the genes for ChIFN1 and ChIFN2 are all located on the short arm of the chicken Z chromosome. This assignment was confirmed by results that showed that DNA from male (ZZ) chickens yielded approximately twofold stronger Southern blot signals with ChIFN1 and ChIFN2 hybridization probes than DNA from females (ZW). Attempts to determine differences in IFN production between male and female chickens failed owing to a high degree of variation in virus-induced IFN expression between individuals of both sexes. Sex linkage of IFN genes was also observed in domestic ducks: fluorescence in situ hybridization of duck metaphase chromosomes with a duck type I IFN probe was confined to the terminal region of the long arm of the Z chromosome. Thus, in contrast to mammals, which have their IFN genes on autosomes, birds have the type I IFN genes on the sex chromosome. Received: 9 January 1998