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Lipopolysaccharide Biosynthesis Without The Lipids: Substrate Recognition For Escherichia Coli Heptosyltransferasei, Daniel J. Czyzyk, Cassie Liu, Erika A. Taylor
Lipopolysaccharide Biosynthesis Without The Lipids: Substrate Recognition For Escherichia Coli Heptosyltransferasei, Daniel J. Czyzyk, Cassie Liu, Erika A. Taylor
Erika A. Taylor, Ph.D.
Heptosyltransferase I (HepI) is responsible for the transfer of l-glycero-d-manno-heptose to a 3-deoxy-α-D-oct-2-ulopyranosonic acid (Kdo) of the growing core region of lipopolysaccharide (LPS). The catalytic efficiency of HepI with the fully deacylated analogue of Escherichia coli HepI LipidA is 12-fold greater than with the fully acylated substrate, with a k(cat)/K(m) of 2.7 × 10(6) M(-1) s(-1), compared to a value of 2.2 × 10(5) M(-1) s(-1) for the Kdo(2)-LipidA substrate. Not only is this is the first demonstration that an LPS biosynthetic enzyme is catalytically enhanced by the absence of lipids, this result has significant implications for downstream enzymes that …
The Growth Suppressing Effects Of Girinimbine On Hepg2 Involve Induction Of Apoptosis And Cell Cycle Arrest, Syam Mohan
The Growth Suppressing Effects Of Girinimbine On Hepg2 Involve Induction Of Apoptosis And Cell Cycle Arrest, Syam Mohan
Syam Mohan
Murraya koenigii is an edible herb widely used in folk medicine. Here we report that girinimbine, a carbazole alkaloid isolated from this plant, inhibited the growth and induced apoptosis in human hepatocellular carcinoma, HepG2 cells. The MTT and LDH assay results showed that girinimbine decreased cell viability and increased cytotoxicity in a dose-and time-dependent manner selectively. Girinimbine-treated HepG2 cells showed typical morphological features of apoptosis, as observed from normal inverted microscopy and Hoechst 33342 assay. Furthermore, girinimbine treatment resulted in DNA fragmentation and elevated levels of caspase-3 in HepG2 cells. Girinimbine treatment also displayed a time-dependent accumulation of the Sub-G(0)/G(1) …