The amino acid sequence of hemoglobin II from the symbiont-harboring clamLucina pectinata

The cytoplasmic hemoglobin II from the gill of the clamLucina pectinata consists of 150 amino acid residues, has a calculatedM _m of 17,476, including heme and an acetylated N-terminal residue. It retains the invariant residues Phe 44 at position CD1 and His 65 at the proximal position F8, as well as the highly conserved Trp 15 at position A12 and Pro 38 at position C2. The most likely candidate for the distal residue at position E7, based on the alignment with other globins, is Gln 65. However, optical and EPR spectroscopic studies of the ferri Hb II (Kraus, D. W., Wittenberg, J. B., Lu, J. F., and Peisach, J.,J. Biol. Chem. 265, 16054–16059, 1990) have implicated a tyrosinate oxygen as the distal ligand. Modeling of theLucina Hb II sequence, using the crystal structure of sperm whale aquometmyoglobin, showed that Tyr 30 substituting for the Leu located at position B10 can place its oxygen within 2.8 Å of the water molecule occupying the distal ligand position. This structural alteration is facilitated by the coordinate mutation of the residue at position CD4, from Phe 46 in the sperm whale myoglobin sequence to Leu 47 inLucina Hb II.     

The complete amino acid sequence of porcine gastrotropin, an ileal protein which stimulates gastric acid and pepsinogen secretion

The stomach is stimulated by an enterooxyntin factor in a delayed response to feeding, resulting in an increase in both gastric acid and pepsinogen secretion. We have previously reported on the identity of such a factor from the porcine ileum (Wider, M. D., Vinik, A. I., and Heldsinger, A. (1984) Endocrinology 115, 1484-1491). This protein, termed gastrotropin, is localized to the distal region of the ileum where it constitutes less than 0.1% of the cytosolic protein. We have completed the primary structure of porcine gastrotropin by Edman degradation and mass spectrometry. Gastrotropin (Mr = 14,054) contains 127 amino acid residues and has a blocked (acetylated) alanine at its NH2 terminus. The sequence of porcine gastrotropin is similar to rat liver fatty acid-binding protein (FABP), with 44 of 127 residues being identical (35%). Homology with other members of the FABP family is significantly less apparent, with the order of similarity being liver FABP greater than heart FABP greater than retinol-binding protein greater than intestine FABP. The sequences of the NH2-terminal regions of these proteins account for virtually all of the homology; there are 9 conserved residues common to all five proteins. Gastrotropin represents the first member of the FABP family which has an extracellular function.     

RepSeq – A database of amino acid repeats present in lower eukaryotic pathogens

Background  

Amino acid repeat-containing proteins have a broad range of functions and their identification is of relevance to many experimental biologists. In human-infective protozoan parasites (such as the Kinetoplastid and Plasmodium species), they are implicated in immune evasion and have been shown to influence virulence and pathogenicity. RepSeq is a new database of amino acid repeat-containing proteins found in lower eukaryotic pathogens. The RepSeq database is accessed via a web-based application which also provides links to related online tools and databases for further analyses.     

Drosophila Cornichon acts as cargo receptor for ER export of the TGFalpha-like growth factor Gurken

Drosophila Cornichon (Cni) is the founding member of a conserved protein family that also includes Erv14p, an integral component of the COPII-coated vesicles that mediate cargo export from the yeast endoplasmic reticulum (ER). During Drosophila oogenesis, Cni is required for transport of the TGFalpha growth factor Gurken (Grk) to the oocyte surface. Here, we show that Cni, but not the second Drosophila Cni homologue Cni-related (Cnir), binds to the extracellular domain of Grk, and propose that Cni acts as a cargo receptor recruiting Grk into COPII vesicles. Consequently, in the absence of Cni function, Grk fails to leave the oocyte ER. Proteolytic processing of Grk still occurs in cni mutant ovaries, demonstrating that release of the active growth factor from its transmembrane precursor occurs earlier during secretory transport than described for the other Drosophila TGFalpha homologues. Massive overexpression of Grk in a cni mutant background can overcome the requirement of Grk signalling for cni activity, confirming that cni is not essential for the production of the functional Grk ligand. However, the rescued egg chambers lack dorsoventral polarity. This demonstrates that the generation of temporally and spatially precisely coordinated Grk signals cannot be achieved by bulk flow secretion, but instead has to rely on fast and efficient ER export through cargo receptor-mediated recruitment of Grk into the secretory pathway.     

Welcome to this edition of the JoCB Bulletin containing items of information for the Chemical Biology Community

JOCB Bulletin

Welcome to this edition of the JoCB Bulletin containing items of information for the Chemical Biology Community     

CD11cCD8 T cells: Two-faced adaptive immune regulators

Regulatory cells, important controllers of immune homeostasis, carry out a multi-pronged attack by deleting overactive pathogenic immune cells, by supporting anergy, and by blocking effector functions, thereby contributing to the amelioration of disease. CD8⁺ T cells co-expressing CD11c are a new addition to the growing list of regulatory cells. Naïve mice harbor CD11c-expressing CD8⁺ T cells (<3%) that expand further in an antigen-dependent manner. Although activated CD11c⁺CD8⁺ T cells express suppressive cytokines such as IL-10 and TGF-β, their production of IFN-γ is central to their immune suppressive potential. The CD11c⁺CD8⁺ T cells target pathogenic CD4⁺ T cells in a cell-cell contact dependent manner via IDO- and GCN2-dependent mechanisms. Adoptive transfer of activated CD11c⁺CD8⁺ T cells halts the progression of autoimmune rheumatoid arthritis and colitis. However, in certain virus and cancer models the CD11c⁺CD8⁺ T cells assume the role of immune effectors, boosting immune potential. This seemingly dual nature of these cells - exerting regulatory vs. effector activities - makes them an attractive therapeutic target. In this review, we discuss the discovery, origins and developmental requirements of CD11c⁺CD8⁺cells, and the basis of their immuno-suppressive and effector potentials.     

Expression of mammalian GPCRs in C. elegans generates novel behavioural responses to human ligands

Background  

G-protein-coupled receptors (GPCRs) play a crucial role in many biological processes and represent a major class of drug targets. However, purification of GPCRs for biochemical study is difficult and current methods of studying receptor-ligand interactions involve in vitro systems. Caenorhabditis elegans is a soil-dwelling, bacteria-feeding nematode that uses GPCRs expressed in chemosensory neurons to detect bacteria and environmental compounds, making this an ideal system for studying in vivo GPCR-ligand interactions. We sought to test this by functionally expressing two medically important mammalian GPCRs, somatostatin receptor 2 (Sstr2) and chemokine receptor 5 (CCR5) in the gustatory neurons of C. elegans.     

Biological Control of Sheep Parasites using Duddingtonia flagrans: Trials on Commercial Farms in Sweden

   

Trials were conducted on 3 commercial sheep farms in Sweden to assess the effect of administering spores of the nematode trapping fungus, Duddingtonia flagrans, together with supplementary feed to lactating ewes for the first 6 weeks from turn-out on pastures in spring. Also control groups of ewes, receiving only feed supplement, were established on all 3 farms. Groups were monitored by intensive parasitological investigation. The ewes and their lambs were moved in late June to saved pastures for summer grazing, the lambs receiving an anthelmintic treatment at this time. After approximately 6 weeks on summer pasture the lambs were weaned, treated a second time with anthelmintic, and returned to their original lambing pastures for finishing. Decisions as to when lambs were to be marketed were entirely at the discretion of the farmer co-operators. No difference in lamb performance was found between the two treatments on all three farms. This was attributed to the high levels of nutrition initially of the ewes limiting their post-partum rise in nematode faecal egg counts in spring, which in turn resulted in low levels of nematode infection on pastures throughout the autumn period. Additionally, pastures were of good quality for the lambs during the finishing period, so they grew at optimal rates as far as the farmers were concerned.