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1.
Mol Microbiol ; 32(5): 977-89, 1999 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-10361300

RESUMEN

We have previously described HpuAB, a two-component receptor that mediates binding to haemoglobin (Hb), haemoglobin-haptoglobin (Hb-Hp) and apo-haptoglobin (Hp). In this communication, we constructed non-polar mutations in the hpuA and hpuB loci to examine the individual roles of HpuA and HpuB. Our results indicate that both HpuA and HpuB are required for the acquisition of Fe from Hb and Hb-Hp. We isolated Hb utilization-positive (Hb+) variants of our Hb utilization-negative (Hb-) hpu mutants at a frequency of 10(-3) and demonstrated that the Hb+ phenotype resulted from the expression of a second Hb receptor, HmbR. Expression of HmbR in DNM2 was found to be controlled by translational frameshifting involving a polyguanine (G) tract located within the hmbR locus. The hpuA locus also contains a poly(G) tract, which suggested that meningococci could phase vary each Hb receptor independently by slip-strand mispairing in the poly(G) tracts found in hpuA and hmbR. Thus, we isolated a naturally occurring Hb- variant of DNM2, designated DNM2 Hb-, which did not express either HpuAB or HmbR. Hb+ variants of DNM2Hb- were selected and examined for HpuAB and HmbR expression. In each instance, acquisition of HpuAB or HmbR expression was correlated with phase variation in the poly(G) tract of each Hb receptor.


Asunto(s)
Proteínas de la Membrana Bacteriana Externa/metabolismo , Hemoglobinas/metabolismo , Hierro/metabolismo , Neisseria meningitidis/metabolismo , Receptores de Superficie Celular/metabolismo , Proteínas de la Membrana Bacteriana Externa/genética , Proteínas Bacterianas/metabolismo , Secuencia de Bases , Western Blotting , Haptoglobinas/metabolismo , Datos de Secuencia Molecular , Mutagénesis Insercional , Neisseria meningitidis/genética , Neisseria meningitidis/crecimiento & desarrollo , Receptores de Superficie Celular/genética
2.
J Endocrinol ; 148(1): 19-25, 1996 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-8568467

RESUMEN

Differing risk factors between men and women for a number of vascular and metabolic diseases have been linked to regional obesity. The differences in the distribution of adipose tissues between men (abdominal or upper-body obesity) and women (gluteal/femoral or lower body obesity) suggest a role for sex steroids in the regional distribution of fat. Previous work from this laboratory has shown the presence of oestrogen receptor (ER) in gluteal, perirenal and omental adipose tissues of ewes with similar physical characteristics to the ER in uterine tissue. The concentration profile for adipose ER was gluteal > perirenal > omental. In this report, we determined the physiological significance of adipose ERs by showing an up-regulation of the progesterone receptor (PR) in adipose tissues after oestrogen treatment in a fashion similar to that seen in a major responsive tissue such as uterus. Using PR antibodies (PR-6 and C-262), Western blot analysis of PR from oestrogen-treated sheep indicated that PR was induced in uterus >>> gluteal adipose > perirenal adipose consistent with the concentration of ER contained in these tissues. PR could not be detected by Western blotting in omental adipose tissue from oestrogen-treated animals or in gluteal, perirenal and omental adipose tissues from untreated animals. Sucrose gradient profiles of progestin (R-5020) binding from uterus and gluteal adipose tissues of oestrogen-treated ewes showed specific binding in both the 5S and 9S regions of the gradient, while perirenal and omental adipose tissue had only the 5S peak. The amount of specific binding was increased with oestrogen treatment in all the tissues. When gluteal adipose tissue cytosol was preincubated with PR antibody (C-262) to prevent binding of ligand and subjected to sucrose gradient analysis, both the 5S and 9S regions were diminished, suggesting that both peaks contained PR. Dilution of uterine cytosol resulted in an increase in the ratio of the 5S to the 9S peak, indicating that the 9S PR complex dissociates at low concentrations; this may be the reason why only the 5S peak was observed in perirenal and omental adipose tissues. These data offer further support for a direct role of sex steroids in regional adipose accretion and metabolism.


Asunto(s)
Tejido Adiposo/metabolismo , Estradiol/farmacología , Receptores de Progesterona/metabolismo , Ovinos/metabolismo , Regulación hacia Arriba , Tejido Adiposo/efectos de los fármacos , Animales , Western Blotting , Centrifugación por Gradiente de Densidad , Citosol/metabolismo , Femenino , Unión Proteica , Útero/metabolismo
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