Novel polysaccharide produced by Azotobacter vinelandii isolated from plant rhizosphere

Summary A strain of Azotobacter vinelandii MTCC 2460 has been isolated from the rhizosphere of the rhizomes of lotus, which produces a novel exopolysaccharide (EPS) having a sugar composition of glucose : galactose : fucose: glucoronic acid (2.2 : 2.7 : 5.6 : 1.6). This composition has not been reported for any species belonging to this genus. The EPS gives high viscosity comparable to xanthan under specific conditions.     

The molecular basis of coupling of translocation and N-glycosylation

Protein translocation and N-glycosylation are essential coordinated cellular processes that are mediated by the translocon and the oligosaccharyl transferase (OT), respectively. The recent identification of several specific interactions between the OT subunits and the translocon provides a molecular basis for the coupling of these two processes. Data suggest that multiple OT isoforms with different affinities for the translocon and ribosome and with heterogeneous subunit composition might exist in the endoplasmic reticulum (ER) membrane, thereby providing a means of regulating protein N-glycosylation.     

Mechanisms in the regulation of aromatase in developing ovary and placenta

During human gestation, the placental syncytiotrophoblast develops the capacity to synthesize large amounts of estrogen from C₁₉-steroids secreted by the fetal adrenals. The conversion of C₁₉-steroids to estrogens is catalyzed by aromatase P450 (P450arom), product of the CYP19 gene. The placenta-specific promoter of the hCYP19 gene lies 100,000 bp upstream of the translation initiation site in exon II. In studies using transgenic mice and transfected human trophoblast cells we have defined a 246-bp region upstream of placenta-specific exon I.1 that mediates placental cell-specific expression. Using transgenic mice, we also observed that as little as 278 bp of DNA flanking the 5′-end of ovary-specific hCYP19 exon IIa was sufficient to target ovary-specific expression. This ovary-specific promoter contains response elements that bind cAMP-response element-binding protein (CREB) and the orphan nuclear receptors SF-1 and LRH-1, which are required for cAMP-mediated stimulation of CYP19 expression in granulosa and luteal cells during the estrous cycle and pregnancy. In this article, we review our studies to define genomic regions and response elements that mediate placenta-specific expression of the hCYP19 gene. The temporal and spatial expression of LRH-1 versus SF-1 in the developing gonad during mouse embryogenesis and in the postnatal ovary also will be considered.