Neurokinin A and B.

The chemical features, pharmacological and biochemical characteristics of novel mammalian tachykinin peptides, neurokinin A and neurokinin B are described and are compared with those of substance P, a representative of tachykinin family.     

Structure of actinoidins A and B

The sequence of the amino acid residues in the peptide chain of aglycone was shown on the basis of the data concerning the splitting of actinoidin aglycon and the products of its partial acid hydrolysis by various methods. It was found that the free COOH-group of actinoidin belonged to he glycine residue of the dioxyphenyl nucleus of actinoidinic amino acid. The site of the actinosamine attachment to aglycon was determined. The final structure of actinoidins A and B is suggested.     

Blood group A and B glycosyltransferases synthesize A and B determinants on different acceptor polyglycosyl peptidesin vitro

The glycosylation of polyglycosyl chains from human erythrocytes by human plasma blood group A and B glycosyltransferases was studied in order to clarify why human blood group AB erythrocyte polyglycosyl peptides carry only either A or B determinants [Eur J Biochem (1981) 113:259–65].The blood group A transferase was able to add radioactiveN-acetylgalactosamine from labeled UDP-N-acetylgalactosamine to B-type erythrocytes which had been treated with -galactosidase in order to cleave the B determinant sugar from the erythrocytes. This suggests that the enzymes specified by theA andB genes utilize the same acceptor molecules on erythrocyte membranes. Polyglycosyl peptides isolated from blood group B erythrocytes acted as acceptors for blood group A glycosyltransferase and the generation of hybrid structures containing both A and B determinants was demon-strated. When blood group O polyglycosyl peptides were used as acceptors in the simultaneous presence of both blood group A and B glycosyltransferases, however, the A and B determinant sugars were found in different polyglycosyl peptides. It is suggested that the enzyme-acceptor complex does not dissociate until the final number of determinants has been added.     

Contributions of A2A and A2B adenosine receptors in coronary flow responses in relation to the KATP channel using A2B and A2A/2B double-knockout mice

Adenosine plays a role in physiological and pathological conditions, and A(2) adenosine receptor (AR) expression is modified in many cardiovascular disorders. In this study, we elucidated the role of the A(2B)AR and its relationship to the A(2A)AR in coronary flow (CF) changes using A(2B) single-knockout (KO) and A(2A/2B) double-KO (DKO) mice in a Langendorff setup. We used two approaches: 1) selective and nonselective AR agonists and antagonists and 2) A(2A)KO and A(2B)KO and A(2A/2B)DKO mice. BAY 60-6583 (a selective A(2B) agonist) had no effect on CF in A(2B)KO mice, whereas it significantly increased CF in wild-type (WT) mice (maximum of 23.3 ± 9 ml·min(-1)·g(-1)). 5'-N-ethylcarboxamido adenosine (NECA; a nonselective AR agonist) increased CF in A(2B)KO mice (maximum of 34.6 ± 4.7 ml·min(-1)·g(-1)) to a significantly higher degree compared with WT mice (maximum of 23.1 ± 2.1 ml·min(-1)·g(-1)). Also, CGS-21680 (a selective A(2A) agonist) increased CF in A(2B)KO mice (maximum of 29 ± 1.9 ml·min(-1)·g(-1)) to a significantly higher degree compared with WT mice (maximum of 25.1 ± 2.3 ml·min(-1)·g(-1)). SCH-58261 (an A(2A)-selective antagonist) inhibited the NECA-induced increase in CF to a significantly higher degree in A(2B)KO mice (19.3 ± 1.6 vs. 0.5 ± 0.4 ml·min(-1)·g(-1)) compared with WT mice (19 ± 3.5 vs. 3.6 ± 0.5 ml·min(-1)·g(-1)). NECA did not induce any increase in CF in A(2A/2B)DKO mice, whereas a significant increase was observed in WT mice (maximum of 23.1 ± 2.1 ml·min(-1)·g(-1)). Furthermore, the mitochondrial ATP-sensitive K(+) (K(ATP)) channel blocker 5-hydroxydecanoate had no effect on the NECA-induced increase in CF in WT mice, whereas the NECA-induced increase in CF in WT (17.6 ± 2 ml·min(-1)·g(-1)), A(2A)KO (12.5 ± 2.3 ml·min(-1)·g(-1)), and A(2B)KO (16.2 ± 0.8 ml·min(-1)·g(-1)) mice was significantly blunted by the K(ATP) channel blocker glibenclamide (to 0.7 ± 0.7, 2.3 ± 1.1, and 0.9 ± 0.4 ml·min(-1)·g(-1), respectively). Also, the CGS-21680-induced (22 ± 2.3 ml·min(-1)·g(-1)) and BAY 60-6583-induced (16.4 ± 1.60 ml·min(-1)·g(-1)) increase in CF in WT mice was significantly blunted by glibenclamide (to 1.2 ± 0.4 and 1.8 ± 1.2 ml·min(-1)·g(-1), respectively). In conclusion, this is the first evidence supporting the compensatory upregulation of A(2A)ARs in A(2B)KO mice and demonstrates that both A(2A)ARs and A(2B)ARs induce CF changes through K(ATP) channels. These results identify AR-mediated CF responses that may lead to better therapeutic approaches for the treatment of cardiovascular disorders.     

Absolute configurations of integracins A, B, and 15'-dehydroxy-integracin B

Integracins A (1) and B (2), potent HIV-1 integrase inhibitors, and 15'-dehydroxy-integracin B (3) were isolated for the first time from Chinese mangrove plant Sonneratia hainanensis. Their absolute configurations were determined by the Mosher's method and specific rotation analysis of alcohols (6 and 7) obtained from integracin A in two steps and by chemical correlation. Integracin A (1) also exhibited significant cytotoxicity against the tumor cell lines HepG2 and NCI-H460 with both 100% inhibitions at 25 μg/ml.     

Toxins A and B of Clostridium difficile

Abstract: The toxins produced by Clostridium difficile share several functional properties with other bacterial toxins, like the heat-labile enterotoxin of Escherichia coli and cholera toxin. However, functional and structural differences also exist. Like cholera toxin, their main target is the disruption of the microfilaments in the cell. However, since these effects are not reversible, as found with cholera toxin, additional mechanisms add to the cytotoxic potential of these toxins. Unlike most bacterial toxins, which are built from two structurally and functionally different small polypeptide chains, the functional and binding properties of the toxins of C. difficile are confined within one large polypeptide chain, making them the largest bacterial toxins known so far.     

A Role for Stefin B (Cystatin B) in Inflammation and Endotoxemia

Stefin B (cystatin B) is an endogenous cysteine cathepsin inhibitor, and the loss-of-function mutations in the stefin B gene were reported in patients with Unverricht-Lundborg disease (EPM1). In this study we demonstrated that stefin B-deficient (StB KO) mice were significantly more sensitive to the lethal LPS-induced sepsis and secreted higher amounts of pro-inflammatory cytokines IL-1β and IL-18 in the serum. We further showed that increased caspase-11 gene expression and better pro-inflammatory caspase-1 and -11 activation determined in StB KO bone marrow-derived macrophages resulted in enhanced IL-1β processing. Pretreatment of macrophages with the cathepsin inhibitor E-64d did not affect secretion of IL-1β, suggesting that the increased cathepsin activity determined in StB KO bone marrow-derived macrophages is not essential for inflammasome activation. Upon LPS stimulation, stefin B was targeted into the mitochondria, and the lack of stefin B resulted in the increased destabilization of mitochondrial membrane potential and mitochondrial superoxide generation. Collectively, our study demonstrates that the LPS-induced sepsis in StB KO mice is dependent on caspase-11 and mitochondrial reactive oxygen species but is not associated with the lysosomal destabilization and increased cathepsin activity in the cytosol.     

A high-density consensus map of A and B wheat genomes

A durum wheat consensus linkage map was developed by combining segregation data from six mapping populations. All of the crosses were derived from durum wheat cultivars, except for one accession of T. ssp. dicoccoides. The consensus map was composed of 1,898 loci arranged into 27 linkage groups covering all 14 chromosomes. The length of the integrated map and the average marker distance were 3,058.6 and 1.6?cM, respectively. The order of the loci was generally in agreement with respect to the individual maps and with previously published maps. When the consensus map was aligned to the deletion bin map, 493 markers were assigned to specific bins. Segregation distortion was found across many durum wheat chromosomes, with a higher frequency for the B genome. This high-density consensus map allowed the scanning of the genome for chromosomal rearrangements occurring during the wheat evolution. Translocations and inversions that were already known in literature were confirmed, and new putative rearrangements are proposed. The consensus map herein described provides a more complete coverage of the durum wheat genome compared with previously developed maps. It also represents a step forward in durum wheat genomics and an essential tool for further research and studies on evolution of the wheat genome.     

Human B and T lymphocytes convert leukotriene A4 into leukotriene B4

Incubation of human tonsillar B lymphocytes and peripheral blood T lymphocytes with leukotriene A4 led to the formation of leukotriene B4. The purity of these cell suspensions was more than 99%, containing less than 0.5% monocytes. Incubation of purified B or T lymphocytes with the calcium ionophore A23187 did not lead to the formation of any detectable amounts of leukotrienes. Several established cell lines of B and T lymphocytic origin were also found to convert leukotriene A4 into leukotriene B4, showing that monoclonal lymphocytic cells possess leukotriene A4 hydrolase activity.     

Lamin A, lamin B, and lamin B receptor analogues in yeast

Previous studies have shown that turkey erythrocyte lamin B is anchored to the nuclear envelope via a 58-kD integral membrane protein termed p58 or lamin B receptor (Worman H. J., J. Yuan, G. Blobel, and S. D. Georgatos. 1988. Proc. Natl. Acad. Sci. USA. 85:8531-8534). We now identify a p58 analogue in the yeast Saccharomyces cerevisiae. Turkey erythrocyte lamin B binds to yeast urea-extracted nuclear envelopes with high affinity, associating predominantly with a 58-kD polypeptide. This yeast polypeptide is recognized by polyclonal antibodies against turkey p58, partitions entirely with the nuclear fraction, remains membrane bound after urea extraction of the nuclear envelopes, and is structurally similar to turkey p58 by peptide mapping criteria. Using polyclonal antibodies against turkey erythrocyte lamins A and B, we also identify two yeast lamin forms. The yeast lamin B analogue has a molecular mass of 66 kD and is structurally related to erythrocyte lamin B. Moreover, the yeast lamin B analogue partitions exclusively with the nuclear envelope fraction, is quantitatively removed from the envelopes by urea extraction, and binds to turkey lamin A and vimentin. As many higher eukaryotic lamin B forms, the yeast analogue is chemically heterogeneous comprising two serologically related species with different charge characteristics. Antibodies against turkey lamin A detect a 74-kD yeast protein, slightly larger than the turkey lamin A. It is more abundant than the yeast lamin B analogue and partitions between a soluble cytoplasmic fraction and a nuclear envelope fraction. The yeast lamin A analogue can be extracted from the nuclear envelope by urea, shows structural similarity to turkey and rat lamin A, and binds to isolated turkey lamin B. These data indicate that analogues of typical nuclear lamina components (lamins A and B, as well as lamin B receptor) are present in yeast and behave as their vertebrate counterparts.