Phenotype-genotype correlation in familial Mediterranean fever: evidence for an association between Met694Val and amyloidosis.
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Familial Mediterranean fever (FMF) is an autosomal recessive disease characterised by recurrent attacks of inflammation of serosal membranes. Amyloidosis is the most severe complication of the disease. The aim of this study was to investigate the genotype-phenotype correlation and specifically the association between amyloidosis and the four common mutations in exon 10 of the gene causing FMF (MEFV) in a total of 83 FMF families from three ethnic groups: North African Jews, Armenians and Turks. A significant association was found between amyloidosis and the specific mutation at the MEFV gene: Met694Val (RR = 1.41, P = 0.02). Amyloidosis was present in 18 out of 87 homozygous FMF patients (20.7%) and in only two out of the 41 compound heterozygous FMF patients (4.9%). No patients carrying other mutations had amyloidosis. There was no significant association between the various mutations and the type or severity of the FMF symptoms. This finding underscores the importance of performing molecular studies on all suspect FMF patients. In addition to providing accurate diagnosis, these tests allow identification of presymptomatic genetically affected individuals, detection of carriers and assessment of the risk for amyloidosis in later life. (+info)
Ovine chorionic somatomammotrophin (oCS) production by isolated cotyledon cells from sheep in early and mid gestation: auto-regulation by recombinant oCS.
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We report the ability of sheep placental cotyledonary cells, isolated at different periods of pregnancy (40 to 90 days) to produce ovine chorionic somatomammotrophin (oCS) in in vitro culture conditions. This oCS production increased gradually with stage of pregnancy. Endogenous oCS net production by isolated placental cells was increased, in a dose-dependent manner, by addition of recombinant oCS (roCS). This effect was not observed after addition of recombinant ovine growth hormone. The roCS effect was more potent on cells collected during early pregnancy. Specific immunoprecipitation of oCS revealed that roCS treatment was associated with an increased dose-dependent incorporation of [35S]methionine-[35S]cysteine. These findings provide evidence that oCS may act in a paracrine/autocrine manner to up-regulate its own production during early gestation. We suggest that this autoregulation may be associated with morphological and functional differentiation of the trophoblast during the growth of the placenta. (+info)
Determinants of fasting and post-methionine homocysteine levels in families predisposed to hyperhomocysteinemia and premature vascular disease.
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Elevated plasma total homocysteine (tHcy) levels, either measured in the fasting state or after oral methionine loading, are associated with an increased risk of atherothrombotic disease. Fasting and post-methionine hyperhomocysteinemia (HHC) overlap to a limited extent; both can occur as familial traits. We investigated determinants of fasting, postmethionine and delta (ie, post-methionine minus fasting levels) tHcy levels in 510 subjects of 192 HHC-prone families including 161 patients with clinical vascular disease and 349 without vascular disease. We focused on tHcy levels in relation to levels of vitamin B12, B6 and folate and the methylenetetrahydrofolate reductase (MTHFR) C677T mutation. Multivariate linear analyses adjusted for the presence of vascular disease showed that fasting tHcy was significantly related to folate and vitamin B12, and the presence of the MTHFR TT genotype and the T allele, and to age, smoking habits, and serum levels of creatinine. Both post-methionine and delta tHcy levels were related to serum folate levels, and the presence of the MTHFR TT genotype and the T allele, and to postmenopausal status, and body mass index. An interaction was found between MTHFR TT genotype and serum folate levels for both fasting and post-methionine tHcy, ie, for a given decrease in serum folate, homocysteine levels increased more in subjects with the TT genotype than in those with the CC genotype. Fasting, post-methionine and delta tHcy were higher in patients with vascular disease than in their healthy siblings, but these levels were less dependent on serum folate levels (P<0.05), whereas the effect of MTHFR genotype was stronger (P=0.01). This study found evidence that post-methionine and delta tHcy levels are not only influenced by factors affecting homocysteine transsulfuration but also by factors that affect remethylation. The explained variances of fasting, post-methionine and delta tHcy were 49%, 62%, and 78%, respectively. We also found evidence, in patients with premature vascular disease but not in their healthy siblings, for a factor that increases tHcy levels but weakens the normal inverse relation between folate and tHcy and amplifies the effect of the MTHFR genotype. (+info)
Homocysteine--a pathophysiological cornerstone in obstetrical and gynaecological disorders?
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Homocysteine, a product of the methionine cycle, is known to play an important role in cardiovascular diseases, neurological disorders and embryology, and in very important, fast growing fields concerning obstetrics and gynaecology. Therefore, we attempted an actual overview on possible obstetrical and gynaecological disorders as a consequence of an impaired methionine cycle. We tried to evaluate all mechanisms concerning homocysteine metabolism in order to look for hypothetical possibilities of therapeutic interventions. Using MEDLINE starting in January 1966, a search was conducted for articles published in which homocysteine was included as a subject heading or a text word. This search was also specified in combination with other key words such as obstetrics, pregnancy, gynaecology and cancer. Additional sources were identified through cross-referencing. All sources found were examined with regard to providing substantial information on our topic. The information obtained was divided into articles dealing with homocysteine and the methionine cycle itself, homocysteine and pregnancy, and homocysteine and hormones, including menopause, hormone replacement therapy and oral contraceptives. Another group was concerned with other special gynaecological aspects of the methionine cycle. We suggest that elevated concentrations of homocysteine could be a marker and perhaps a cause of, or contributive to, a wide range of obstetrical and gynaecological disorders. (+info)
Fasting and post-methionine homocysteine levels in NIDDM. Determinants and correlations with retinopathy, albuminuria, and cardiovascular disease.
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OBJECTIVE: The increased cardiovascular risk in subjects with NIDDM is partly explained by an association with established risk factors like hypertension, dyslipidemia, and obesity. Mild hyperhomocysteinemia has emerged as a new risk factor for cardiovascular disease. The purpose of this study was to assess its role in NIDDM. RESEARCH DESIGN AND METHODS: We studied predictors of homocysteine levels and correlations between homocysteine and (micro-)albuminuria, retinopathy, and history of cardiovascular disease in normotensive NIDDM subjects under stable metabolic control. This was done in 85 NIDDM subjects by measuring fasting and post-methionine-loading homocysteine levels together with blood pressure, BMI, serum cholesterol, triglyceride, HDL cholesterol, folate, vitamin B12, pyridoxal-5-phosphate, HbA1c, and (micro-)albuminuria and creatinine clearance in triplicate 24-h urine samples. The relationship between micro- and macrovascular complications and fasting homocysteine only was studied in an additional 65 subjects, giving a total of 150 subjects. RESULTS: In multiple regression analysis, significant (P < 0.05) predictors of fasting homocysteine were low-normal values of creatinine clearance (threshold effect at < 80 ml.min-1 .1.73 m-2), folate (< 20 nmol/l), and vitamin B12 (< 350 pmol/l), and postmenopausal status in women. Determinants of post-methionine homocysteine were pyridoxal-5-phosphate levels < 80 nmol/l, creatinine clearance, and sex (higher levels in women). Hyperhomocysteinemia did not cluster with other cardiovascular risk factors, like hypertension, obesity, or dyslipidemia. Regarding cardiovascular complications, fasting homocysteine, but not post-methionine homocysteine, was higher in subjects with a history of cardiovascular disease. There was a stepwise increase in the prevalence of subjects with cardiovascular disease with increasing fasting homocysteine. The prevalence of cardiovascular disease was 19.4% in the bottom quartile of fasting homocysteine, versus 55.0% in the top quartile (P for trend < 0.01). Neither fasting homocysteine nor post-methionine homocysteine correlated with (micro-)albuminuria or with retinopathy. CONCLUSIONS: The findings suggest that homocysteine levels in NIDDM rise even with modest deterioration of renal function and when vitamin status is in the low to low-normal range. Fasting homocysteine correlates with macrovascular disease, but we found no evidence of a correlation with retinopathy or (micro-)albuminuria. Post-methionine homocysteine levels do not show a correlation with micro- or macrovascular complications. (+info)
Expression, purification, and crystallography of the conserved methionine-rich domain of human signal recognition particle 54 kDa protein.
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Protein SRP54 is an essential component of eukaryotic signal recognition particle (SRP). The methionine-rich M-domain (SRP54M or 54M) interacts with the SRP RNA and is also involved in the binding to signal peptides of secretory proteins during their targeting to cellular membranes. To gain insight into the molecular details of SRP-mediated protein targeting, we studied the human 54M polypeptide. The recombinant human protein was expressed successfully in Escherichia coli and was purified to homogeneity. Our studies determined the sites that were susceptible to limited proteolysis, with the goal to design smaller functional mutant derivatives that lacked nonessential amino acid residues from both termini. Of the four polypeptides produced by V8 protease or chymotrypsin, 54MM-2 was the shortest (120 residues; Mr = 13,584.8), but still contained the conserved amino acids suggested to associate with the signal peptide or the SRP RNA. 54MM-2 was cloned, expressed, purified to homogeneity, and was shown to bind human SRP RNA in the presence of protein SRP19, indicating that it was functional. Highly reproducible conditions for the crystallization of 54MM-2 were established. Examination of the crystals by X-ray diffraction showed an orthorhombic unit cell of dimensions a = 29.127 A, b = 63.693 A, and c = 129.601 A, in space group P2(1)2(1)2(1), with reflections extending to at least 2.0 A. (+info)
The quiescent-cell expression system for protein synthesis in Escherichia coli.
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The quiescent-cell expression system is a radical alternative to conventional fermentation for protein overproduction in Escherichia coli. It is dependent on the controlled overexpression of a small RNA called Rcd in hns mutant strains to generate nongrowing, quiescent cells which are not nutrient limited. Quiescent cells no longer produce biomass and have their metabolic resources channelled toward the expression of plasmid-based genes. The biosynthetic capacity of the system is demonstrated by its ability to express chloramphenicol acetyltransferase to more than 40% of total cell protein. Quiescent cells may provide an ideal environment for the expression of toxic as well as benign proteins. (+info)
Methionine adenosyltransferase S-nitrosylation is regulated by the basic and acidic amino acids surrounding the target thiol.
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S-Adenosylmethionine serves as the methyl donor for many biological methylation reactions and provides the propylamine group for the synthesis of polyamines. S-Adenosylmethionine is synthesized from methionine and ATP by the enzyme methionine adenosyltransferase. The cellular factors regulating S-adenosylmethionine synthesis have not been well defined. Here we show that in rat hepatocytes S-nitrosoglutathione monoethyl ester, a cell-permeable nitric oxide donor, markedly reduces cellular S-adenosylmethionine content via inactivation of methionine adenosyltransferase by S-nitrosylation. Removal of the nitric oxide donor from the incubation medium leads to the denitrosylation and reactivation of methionine adenosyltransferase and to the rapid recovery of cellular S-adenosylmethionine levels. Nitric oxide inactivates methionine adenosyltransferase via S-nitrosylation of cysteine 121. Replacement of the acidic (aspartate 355) or basic (arginine 357 and arginine 363) amino acids located in the vicinity of cysteine 121 by serine leads to a marked reduction in the ability of nitric oxide to S-nitrosylate and inactivate hepatic methionine adenosyltransferase. These results indicate that protein S-nitrosylation is regulated by the basic and acidic amino acids surrounding the target cysteine. (+info)