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101.
102.
Van Eck M Hoekstra M Out R Bos IS Kruijt JK Hildebrand RB Van Berkel TJ 《Journal of lipid research》2008,49(1):136-146
Scavenger receptor class B type I (SR-BI) functions as an HDL receptor that promotes the selective uptake of cholesteryl esters (CEs). The physiological role of SR-BI in VLDL metabolism, however, is largely unknown. SR-BI deficiency resulted in elevated VLDL cholesterol levels, both on chow diet and upon challenge with high-cholesterol diets. To specifically elucidate the role of SR-BI in VLDL metabolism, the plasma clearance and hepatic uptake of (125)I-beta-VLDL were studied in SR-BI(+/+) and SR-BI(-/-) mice. At 20 min after injection, 66 +/- 2% of the injected dose was taken up by the liver in SR-BI(+/+) mice, as compared with only 22 +/- 4% (P = 0.0007) in SR-BI(-/-) mice. In vitro studies established that the B(max) of (125)I-beta-VLDL binding was reduced from 469 +/- 30 ng/mg in SR-BI(+/+) hepatocytes to 305 +/- 20 ng/mg (P = 0.01) in SR-BI(-/-) hepatocytes. Both in vivo and in vitro, limited to no selective uptake of CEs from beta-VLDL was found. Interestingly, HDL effectively competed for the association of beta-VLDL in the presence as well as in the absence of SR-BI, indicating a second common recognition site. In conclusion, SR-BI plays an important physiological role in the metabolism of VLDL (remnants). 相似文献
103.
Catalase plays a central role in plant stress responses but is highly susceptible to photoinhibition. A rice catalase-B protein
avoiding photoinhibition was developed by mutagenesis of specific amino acids: Leu-189 to Trp-189 and His-225 to Thr-225 and
then recombinantly expressed in E. coli. In addition, the site specific mutation also induced 2–2.5-fold increase in enzyme velocity with high affinity for its substrate
and showed nearly a 3-fold lower K
m
than the wild protein. These characteristic of mutated rice catalase-B is highly promising in transgenic research to increase
plant productivity under stress conditions. 相似文献
104.
Nidhi Batra Manuel A. Riquelme Sirisha Burra Rekha Kar Sumin Gu Jean X. Jiang 《The Journal of biological chemistry》2014,289(15):10582-10591
Connexin (Cx) 43 hemichannels in osteocytes are thought to play a critical role in releasing bone modulators in response to mechanical loading, a process important for bone formation and remodeling. However, the underlying mechanism that regulates the opening of mechanosensitive hemichannels is largely unknown. We have recently shown that Cx43 and integrin α5 interact directly with each other, and activation of PI3K appears to be required for Cx43 hemichannel opening by mechanical stimulation. Here, we show that mechanical loading through fluid flow shear stress (FFSS) increased the level of active AKT, a downstream effector of PI3K, which is correlated with the opening of hemichannels. Both Cx43 and integrin α5 are directly phosphorylated by AKT. Inhibition of AKT activation significantly reduced FFSS-induced opening of hemichannels and disrupted the interaction between Cx43 and integrin α5. Moreover, AKT phosphorylation on Cx43 and integrin α5 enhanced their interaction. In contrast to the C terminus of wild-type Cx43, overexpression of the C-terminal mutant containing S373A, a consensus site previously shown to be phosphorylated by AKT, failed to bind with α5 and hence could not inhibit hemichannel opening. Together, our results suggest that AKT activated by FFSS directly phosphorylates Cx43 and integrin α5, and Ser-373 of Cx43 plays a predominant role in mediating the interaction between these two proteins and Cx43 hemichannel opening, a crucial step to mediate the anabolic function of mechanical loading in the bone. 相似文献
105.
Genetic variability and association of ISSR markers with some biochemical traits in mulberry (Morus spp.) genetic resources available in India 总被引:2,自引:0,他引:2
Prasanta K. Kar Prem P. Srivastava Arvind K. Awasthi S. Raje Urs 《Tree Genetics & Genomes》2008,4(1):75-83
Utilizing intersimple sequence repeat (ISSR) markers, 18 mulberry (Morus spp.) germplasm collections were studied for genetic variability, phylogenetic relationship, and association with protein
and sugar content. The genetic polymorphism exhibited by ISSR primers was 100%, and the genetic diversity recorded among the
mulberry accessions had an average of 0.263 ± 0.094. Dendrogram (unweighted pair group method analysis) clustered the mulberry
accessions into two major groups, one comprised the accessions collected from north or northeast regions of India, and the
other comprised three subclusters and one isolate, i.e., Assamjati, a collection from Assam. Another subcluster contained
accessions collected from Kerala, which belong to Morus indica. These accessions of M. indica from Kerala were found to be genetically diverse from north and northeast India. Multidimensional scaling of the ISSR data
clearly separated the mulberry accessions according to their genetic diversity and protein content. Mulberry accessions were
arbitrarily grouped into three classes viz. very low, moderate, and high in terms of protein and sugar content using standard
statistical programs. Stepwise multiple regression analysis identified four ISSR markers (8351,600, 8355,600, 8222,500, and 8072,500) associated with protein content with highly positive correlation (p < 0.001) with linear curves with high F values (18.055 to 48.674; p < 0.001). In case of sugar content, four ISSR markers viz. 812900, 8171,500, 8261,500, and 8108,000 showed negative correlation. Hence, DNA markers for proteins seem promising and may be used in marker-assisted breeding program. 相似文献
106.
107.
Chromosomal variability in callus culture ofAsparagus racemosus was comparatively higher in the presence of 2,4-D than of NAA. The frequency of polyploid cells was enhanced with the increase
in the concentration of 2,4-D or with the addition of coconut water. Gradual polyploidization with increasing age of the callus
has been recorded. 相似文献
108.
109.
110.
Debasish Kar Satya Deo Pandey Sathi Mallick Mouparna Dutta Anindya S. Ghosh 《The protein journal》2018,37(2):122-131
Escherichia coli PBP5, a DD-carboxypeptidase (DD-CPase), helps in maintaining cell shape and intrinsic β-lactam resistance. Though PBP5 does not have β-lactamase activity under physiological pH, it has a common but shorter Ω-like loop resembling class A β-lactamases. However, such Ω-like loop lacks the key glutamic acid residue that is present in β-lactamases. It is speculated that β-lactamases and DD-CPases might have undergone divergent evolution leading to distinct enzymes with different substrate specificities and functions indicating the versatility of the Ω-loops. Nonetheless, direct experimental evidence favoring the idea is insufficient. Here, aiming to investigate the effect of introducing a glutamic acid residue in the PBP5 Ω-like loop, we substituted A184 to E to create PBP5_A184E. Expression of PBP5_A184E in E. coli ?PBP5 mutant elevates the β-lactam resistance, especially for cephalosporins. However, like PBP5, PBP5_A184E has the ability to complement the aberrantly shaped E. coli septuple PBP mutant indicating an unaffected in vivo DD-CPase activity. Biochemical and bioinformatics analyses have substantiated the dual enzyme nature of the mutated enzyme possessing both DD-CPase and β-lactamase activities. Therefore, substitution of A184 to E of Ω-like loop alone can introduce the cephalosporinase activity in E. coli PBP5 supporting the phenomenon of a single amino acid polymorphism. 相似文献