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At least 271 records · Page 15Linked to original sources
PubMed2006

Triple helix stabilization by covalently linked DNA-bisbenzimidazole conjugate synthesized by maleimide-thiol coupling chemistry.

Tethering of BBZPNH2, an analogue of the Hoechst 33258, with a 14 nucleotide long DNA sequence with the help of succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), a heterobifunctional crosslinking reagent, using DMF/ water as solvent yields a conjugate which effectively stabilizes the triple helix. The above conjugate was hybridized with 26 bp long double stranded (ds) DNA having 14 bp long polypurine-polypyrimidine stretch to form a pyrimidine motif triple helix. The above conjugate increases the thermal stability of both the transitions, that is, triple helix to double helix by 12 degrees C and double helix to single strand transition by 16 degrees C for the triple helix formed with conjugated TFO over the triple helix made from non-conjugated TFO. Fluorescence and circular dichroism spectra recorded at different temperatures confirm the presence of minor groove binding bisbenzimidazole in the AT-rich minor groove of dsDNA even after the major groove bound TFO separates out.

Benzimidazoles↗
PubMed2002

Probing the membrane topology of a subunit of the mitochondrial protein translocase, Tim44, with biotin maleimide.

Tim44 is an essential component of the translocase of the inner mitochondrial membrane (TIM) complex that mediates transport of nuclear encoded mitochondrial precursors across the inner membrane. Here, we have investigated the topology of Tim44 by probing mitochondria with membrane impermeable 3-(N-maleimidopropionyl)biocytin (MPB) followed by the specific immunoprecipitation of modified proteins. Our data indicate that a single cysteine residue, Cys-369, located in the C-terminal domain of the yeast Tim44 is exposed to the mitochondrial intermembrane space.

Amino Acid Sequence↗
PubMed2003

Characterization of maleimide-activated Ca2+ entry in neutrophils.

N-Ethylmaleimide (NEM), a thio-alkylating agent, concentration-dependently stimulated the elevation of [Ca(2+)](i) in rat neutrophils in the presence of external Ca(2+). This effect was not observed in Ca(2+)-free medium and was abrogated by dithiothreitol pretreatment. The application of NEM after cyclopiazonic acid (CPA) stimulated the store-emptying activation of Ca(2+) entry. Unlike CPA-induced cation entry, NEM showed poor uptake of Ba(2+) and Sr(2+) and did not induce Mn(2+) influx. NEM diminished CPA-induced Mn(2+) influx, an effect that was blocked by dithiothreitol. Both Ni(2+) and La(3+) attenuated the elevation of [Ca(2+)](i) in response to NEM; however, greater resistance was observed to Ni(2+) inhibition of NEM-induced Ca(2+) influx than inhibition of store-operated Ca(2+) entry. Both cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL-12,330A) and 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole (SKF-96365), Ca(2+) channel blockers, and calyculin A, an inhibitor of protein serine/threonine phosphatases 1/2, diminished the NEM-induced Ca(2+) entry. Treatment of cells with genistein, a general tyrosine kinase inhibitor, or with wortmannin and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), phosphatidylinositol 3-kinase inhibitors, had no appreciable inhibitory effects on the action of NEM. However, 2-aminoethyldiphenyl borate, an inositol trisphosphate receptor antagonist, enhanced rather than inhibited the [Ca(2+)](i) change in response to NEM. These results indicate that NEM stimulates Ca(2+) entry and regulates Ca(2+) signaling through direct thiol oxidation, bypassing the cellular signal transduction pathway. The NEM-regulated Ca(2+) signal demonstrates characteristics that distinguish it from the store-emptying operation in neutrophils, and therefore represents two distinct modes of Ca(2+) regulation.

Alkylating Agents↗