Hexacoordinate hemoglobins are found in many living organisms ranging from prokaryotes to plants and animals. They are named “hexacoordinate” because of reversible coordination of the heme iron by a histidine side chain located in the heme pocket. This endogenous coordination competes with exogenous ligand binding and causes multiphasic relaxation time courses following rapid mixing or flash photolysis experiments. Previous rapid mixing studies have assumed a steady-state relationship between hexacoordination and exogenous ligand binding that does not correlate with observed time courses for binding. Here, we demonstrate that this assumption is not valid for some hexacoordinate hemoglobins, and that multiphasic time courses are due to an appreciable fraction of pentacoordinate heme resulting from relatively small equilibrium constants for hexacoordination (K H). CO binding reactions initiated by rapid mixing are measured for four plant hexacoordinate hemoglobins, human neuroglobin and cytoglobin, and Synechocystis hemoglobin. The plant proteins, while showing a surprising degree of variability, differ from the others in having much lower values of K H. Neuroglobin and cytoglobin display dramatic biphasic time courses for CO binding that have not been observed using other techniques. Finally, an independent spectroscopic quantification of K H is presented that complements rapid mixing for the investigation of hexacoordination. These results demonstrate that hexacoordination could play a much larger role in regulating affinity constants for ligand binding in human neuroglobin and cytoglobin than in the plant hexacoordinate hemoglobins.
Using in silico methods, several putative phytohormone-responsive cis-elements in the Oryza sativa non-symbiotic haemoglobin (NSHB) 1-4 and Arabidopsis thaliana NSHB1-2 promoters have been identified. An OsNSHB2 promoter::GUS reporter gene fusion shows tissue-specific expression in A. thaliana. GUS expression was observed in roots, the vasculature of young leaves, in flowers, and in the pedicel/stem junction. In transient assays, activity of the OsNSHB2 promoter was significantly up-regulated in the presence of the cytokinin, 6-benzylaminopurine (BA). Deletion analyses indicated that the full-length promoter was required for maximal trans-activation in the presence of cytokinin. Mutation of the single cytokinin-regulated ARR1-binding element abolished promoter activation in response to cytokinin. Constitutive expression of ARR1 under the control of the 35S cauliflower mosaic virus promoter enhanced wild-type OsNSHB2 promoter activity, but had no effect on the activity of the mutated promoter in the absence of cytokinin. However, overexpression of ARR1 in the presence of cytokinin resulted in super-activation of the wild-type promoter. The mutated promoter was only moderately activated in the presence of cytokinin and ARR1, indicating that the OsNSHB2 promoter can be regulated by the ARR1 protein, but requires other cytokinin-induced factors for optimal activation. This is the first report that identifies a trans-acting factor involved in the activation of a NSHB gene.
The food-grade Lactococcus lactis is a potential vector to be used as a live vehicle for the delivery of heterologous proteins for vaccine and pharmaceutical purposes. We constructed a plasmid vector pSVac that harbors a 255-bp single-repeat sequence of the cell wall-binding protein region of the AcmA protein. The recombinant plasmid was transformed into Escherichia coli and expression of the gene fragment was driven by the T7 promoter of the plasmid. SDS-PAGE showed the presence of the putative AcmA' fragment and this was confirmed by Western blot analysis. The protein was isolated and purified using a His-tag affinity column. When mixed with a culture of L. lactis MG1363, ELISA and immunofluorescence assays showed that the cell wall-binding fragment was anchored onto the outer surface of the bacteria. This indicated that the AcmA' repeat unit retained the active site for binding onto the cell wall surface of the L. lactis cells. Stability assays showed that the fusion proteins (AcmA/A1, AcmA/A3) were stably docked onto the surface for at least 5 days. The AcmA' fragment was also shown to be able to strongly bind onto the cell surface of naturally occurring lactococcal strains and Lactobacillus and, with less strength, the cell surface of Bacillus sphericus. The new system designed for cell surface display of recombinant proteins on L. lactis was evaluated for the expression and display of A1 and A3 regions of the VP1 protein of enterovirus 71 (EV71). The A1 and A3 regions of the VP1 protein of EV71 were cloned upstream to the cell wall-binding domains of AcmA protein and successfully expressed as AcmA/A1 and AcmA/A3. Whole-cell ELISA showed the successful display of VP1 protein epitopes of EV71 on the surface of L. lactis. The success of the anchoring system developed in this study for docking the A1 and A3 epitopes of VP1 onto the surface of L. lactis cells opens up the possibilities of peptide and protein display for not only Lactococcus but also for other gram-positive bacteria. This novel way of displaying epitopes on the cell surface of L. lactis and other related organisms should be very useful in the delivery of vaccines and other useful proteins.
Shearman, L.; Mathiesen, M.; Zhou, Y.J.; Arredondo-Peter, R.; Sarath, Gautam; and Klucas, R. V., "Nonsymbiotic hemoglobins in rice are synthesized during germination and in differentiating cell types" (2001 Abstract: Nonsymbiotic hemoglobins (ns-Hbs) previously have been found in monocots and dicots; however, very little is known about the tissue and cell type localization as well as the physiological function(s) of these oxygen-binding proteins. We report the immunodetection and immunolocalization of ns-Hbs in rice (Oryza sativa L.) by Western blotting and in situ confocal laser scanning techniques. Ns-Hbs were detected in soluble extracts of different tissues from the developing rice seedling by immunoblotting. Levels of ns-Hbs increased in the germinating seed for the fi rst six days following imbibition and remained relatively constant thereafter. In contrast, ns-Hb levels decreased during leaf maturation. Roots and mesocotyls contained detectable, but low levels of ns-Hbs. Split-seed experiments revealed that ns-Hbs are synthesized de novo during seed germination and are expressed in the absence of any signal originating from the embryo. Immunolocalization of ns-Hbs by con-focal microscopy indicated the presence of ns-Hbs primarily in differentiated and differentiating cell types of the developing seedling, such as the aleurone, scutellum, root cap cells, sclerenchyma, and tracheary elements. To our knowledge, this is the fi rst report of the specifi c cellular localization of these proteins during seedling development.
Background: Following research demonstrating the effect of the intrauterine environment on childhood health and health in later life, women are encouraged to adopt healthy behaviours during pregnancy in order to promote the health of the fetus. Aim: This research aimed to explore the influences on women's engagement with healthy practices during pregnancy, particularly the effect of maternal—fetal attachment. Methods: This qualitative study used nine semi-structured interviews and one focus group. These were conducted with women who were pregnant or who had recently given birth. Participants were questioned about their attitudes towards and engagement with the health advice they received during pregnancy. Results: The bond felt with their baby was an important influence on women's decisions to adopt healthy behaviours during pregnancy. This bond was created in many ways. Previous studies have found an increase in women's adherence to healthy behaviours as levels of maternal–fetal attachment increase. However, this research found that as women became more bonded to the fetus they became more reassured of its wellbeing, and were less anxious about strictly adhering to healthy diets or abstaining from alcohol. conclusions: If health advice emphasises the wellbeing of the fetus in efforts to improve maternal health behaviour during pregnancy, women may not see its relevance if their embodied experience and diagnostic tests indicate that the fetus is healthy. The health advice offered to women should be sensitive to their personal experiences of pregnancy.
Biomedicine is often presented as the driving force behind improvements in cancer care, with genomics the latest innovation poised to change the meaning, diagnosis, treatment, prevention and lived experience of cancer. Reviewing sociological analyses of a diversity of patient and practitioner experiences and accounts of cancer during the last decade (2007–17), we explore the experiences of, approaches to and understandings of cancer in this period. We identify three key areas of focus: (i) cancer patient experiences and identities; (ii) cancer risk and responsibilities and (iii) bioclinical collectives. We explore these sociological studies of societal and biomedical developments and how sociologists have sought to influence developments in cancer identities, care and research. We end by suggesting that we extend our understanding of innovations in the fields of cancer research to take better account of these wider social and cultural innovations, together with patients, activists' and sociologists' contributions therein.
Since the very earliest studies of scientific communities, we have known that texts and worlds are bound together. One of the most important ways to stabilise, organise and grow a laboratory, a group of scholars, even an entire intellectual community, is to write things down. As for science, so for the social studies of science: Inscriptions is a space for writing, recording and inscribing the most exciting current work in sociological and anthro-
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