The conversion of light to chemical energy by the process of photosynthesis is localized to the thylakoid membrane network in plant chloroplasts. Although several pathways have been described that target proteins into and across the thylakoids, little is known about the origin of this membrane system or how the lipid backbone of the thylakoids is transported and fused with the target membrane. Thylakoid biogenesis and maintenance seem to involve the flow of membrane elements via vesicular transport. Here we show by mutational analysis that deletion of a single gene called VIPP1 (vesicle-inducing protein in plastids 1) is deleterious to thylakoid membrane formation. Although VIPP1 is a hydrophilic protein it is found in both the inner envelope and the thylakoid membranes. In VIPP1 deletion mutants vesicle formation is abolished. We propose that VIPP1 is essential for the maintenance of thylakoids by a transport pathway not previously recognized.
Plant chloroplasts originated from an endosymbiotic event by which an ancestor of contemporary cyanobacteria was engulfed by an early eukaryotic cell and then transformed into an organelle. Oxygenic photosynthesis is the specific feature of cyanobacteria and chloroplasts, and the photosynthetic machinery resides in an internal membrane system, the thylakoids. The origin and genesis of thylakoid membranes, which are essential for oxygenic photosynthesis, are still an enigma. Vipp1 (vesicle-inducing protein in plastids 1) is a protein located in both the inner envelope and the thylakoids of Pisum sativum and Arabidopsis thaliana. In Arabidopsis disruption of the VIPP1 gene severely affects the plant's ability to form properly structured thylakoids and as a consequence to carry out photosynthesis. In contrast, Vipp1 in Synechocystis appears to be located exclusively in the plasma membrane. Yet, as in higher plants, disruption of the VIPP1 gene locus leads to the complete loss of thylakoid formation. So far VIPP1 genes are found only in organisms carrying out oxygenic photosynthesis. They share sequence homology with a subunit encoded by the bacterial phage shock operon (PspA) but differ from PspA by a C-terminal extension of about 30 amino acids. In two cyanobacteria, Synechocystis and Anabaena, both a VIPP1 and a pspA gene are present, and phylogenetic analysis indicates that VIPP1 originated from a gene duplication of the latter and thereafter acquired its new function. It also appears that the C-terminal extension that discriminates VIPP1 proteins from PspA is important for its function in thylakoid formation.
We conclude that total homocysteine and particularly cardiac troponin T are important predictors of mortality in patients with end-stage renal disease, whereas other laboratory variables and baseline disease status have less prognostic value.
Vitamin D3 increases the total 25(OH)D concentration more than vitamin D2. Vitamin D2 supplementation was associated with a decrease in 25(OH)D3, which can explain the different effect on total 25(OH)D.
Purpose: In the present study, we aimed to substantiate the putative significance of angiotensin I^converting enzyme (ACE) on gastric cancer biology by investigating the influence of its gene polymorphism on gastric cancer progression. Experimental Design: Genomic DNA was purified from peripheral blood mononuclear cells or tissue specimens. Amplified ACE gene fragments were separated on agarose gels. D or I alleles were identified by the presence of 190-or 490-bp fragments, respectively. Local expression of ACE was investigated by immunohistochemistry. Results: Twenty-four of 113 (21%) gastric cancer patients had the II, 57 (51%) the ID, and 32 (28%) the DD genotype. The distribution of the ACE genotypes did not differ significantly from the control group of 189 patients without gastric cancer. However, the ACE genotypes correlated with the number of lymph node metastases and the Unio Internationale Contra Cancrum (UICC) tumor stage. Patients with the II genotype had a highly significantly smaller number of lymph node metastases (P < 0.001) and a significantly lower UICC tumor stage (P = 0.01) than patients with the DD genotype. No correlation was found between tumor type, tumor location, local tumor growth, distant metastases, and the ACE genotype. The expression of ACE in gastric cancer was investigated by immunohistochemistry in 100 of 113 patients. ACE was expressed by endothelial cells in all (100%) specimens and by tumor cells in 56 (56%) specimens. Conclusions: Our study shows that ACE is expressed locally in gastric cancer and that the gene polymorphism influences metastatic behavior.
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