We reported previously that lithocholic acid (LCA, 3-α-hydroxy-5-β-cholan-24-oic acid), one of the major compounds in the secondary bile acids, selectively inhibited the activity of mammalian DNA polymerase β (pol β) [Mizushina, Y., Ohkubo, T., Sugawara, F., and Sakaguchi, K. (2000) Biochemistry 39, 12606−12613]. The purpose of this study was to investigate the molecular structural relationship of LCA and its 10 chemically synthesized derivatives. The inhibitory activities of pol β by some derivative compounds were stronger than that by LCA, and these compounds bound tightly to the 8-kDa domain fragment but not to the 31-kDa domain fragment of pol β. Biacore analysis demonstrated that the 8-kDa domain bound selectively to compound 9 (3-α-O-lauroyl-5-β-cholan-24-oic acid), which was the strongest pol β inhibitor tested, as a 1:1 complex with a dissociation constant (Kd) of 1.73 nM. From computer modeling analysis (i.e., molecular dynamics analysis), the 8-kDa domain had two inhibitor binding areas. Three amino acid residues (Lys60, Leu77, and Thr79) of the 8-kDa domain bound to LCA and compound 2 (3-α-methoxy-5-β-cholan-24-oic acid), and four amino acid residues (Leu11, Lys35, His51, and Thr79) of the 8-kDa domain bound to compound 9. From these results, the structure−function relationship among pol β and its selective inhibitors was discussed.
We reported previously that sulfolipids in the sulfoquinovosylacylglycerol class from a fern and an alga are potent inhibitors of DNA polymerase α and β and potent anti‐neoplastic agents. In developing a procedure for chemical synthesis of sulfolipids, we synthesized many derivatives and stereoisomers of sulfoquinovosylmonoacylglycerol (SQMG)/sulfoquinovosyldiacylglycerol (SQDG). Some of these molecules were stronger inhibitors than the SQMG/SQDG originally reported as natural compounds. In this study, we examined the structure‐inhibitory function relationship of synthetic SQMG/SQDG and its relationship to cytotoxic activity. The inhibitory effect is probably mainly dependent on the fatty acid effect, which we reported previously, although each of the SQMG/SQDG was a much stronger inhibitor than the fatty acid alone that was present in the SQMG/SQDG. The inhibitory effect could be influenced by the chain size of fatty acids in the SQMG/SQDG. The sulfate moiety in the quinovose was also important for the inhibition. Lineweaver‐Burk plots of SQMG/SQDG indicated that DNA polymerase α was non‐competitively inhibited, but the SQMG/SQDG were effective as antagonists of both template‐primer DNA‐binding and nucleotide substrate‐binding of DNA polymerase β. The SQMG had an cytotoxic effect, but the SQDG tested did not. The SQDG might not be able to penetrate into cells. Based on these results, we discuss the molecular action of SQMG/SQDG and propose drug design strategies for developing new anti‐neoplastic agents.
The [4+4] polymerization of an unsaturated imine, generated from the condensation of a polyamine and excess acrolein, was investigated. The polyamine was added by micropipet to acrolein, immediately yielding a mixture of the immiscible polymeric material. Microfluidic mixing was used to gradually form the soluble diazacyclooctane polymers. The polymerization reaction ultimately gave an insoluble cationic hydrogel that adhered strongly to anionic compounds on cell surfaces, including sialoglycan, and displayed a high cytotoxicity.
This article corrects: Crystal structure of human dendritic cell inhibitory receptor C-type lectin domain reveals the binding mode with N-glycan, Volume 590, Issue 8, 1280–1288. Article first published online: 6 April 2016. DOI of original article: 10.1002/1873-3468.12162 Table 1 of the article should read:
Amphotericin B, an antifungal drug with a long history of use, forms fungicidal ion-permeable channels across cell membranes. Using solid-state nuclear magnetic resonance spectroscopy and molecular dynamics simulations, we experimentally elucidated the three-dimensional structure of the molecular assemblies formed by this drug in membranes in the presence of fungal sterol, ergosterol. A stable assembly consisting of seven drug molecules was observed to form an ion conductive channel. The structure is somewhat similar to the upper half of the barrel-stave model proposed in the 1970s but substantially different in the number of molecules and in their arrangement. The high-resolution structure explains many previous findings, including structure-activity relationships of the drug, which will be useful for improving drug efficacy and reducing adverse effects.
The polymer-resin hybrid type capture-release purification strategy for oligosaccharide synthesis was renewed as more rapid and straightforward manner. The substrate for N-acetylglucosaminyltransferase V trisaccharide was synthesized rapidly on PEG (poly (ethylene glycol) methyl ether) and purified by use of the strategy.
The in vitro relationship between the human p53 DNA binding domain (p53 DBD) and glycolipids was investigated. We isolated the glycolipid fraction from spinach (Spinacia oleracea L.) and found that the fraction inhibited the double-stranded DNA (dsDNA) binding activity of p53 DBD. Since the fraction contained mainly three glycolipids, monogalactosyl diacylglycerol (MGDG), digalactosyl diacylglycerol (DGDG) and sulfoquinovosyl diacylglycerol (SQDG), and each glycolipid was purified using silica gel column chromatography. Purified SQDG inhibited the activity, however, purified MGDG and DGDG had no influence. In this study, we demonstrated the structure-function relationship between chemically synthetic SQDG and p53 DBD. The major action is probably dependent on the fatty acid effect, although SQDG was a much stronger inhibitor than the fatty acid alone present in SQDG. The inhibitory activity of SQDG was weakened by the R248A mutant of p53 DBD, suggesting that R248 in the dsDNA binding site of p53 must be important for the inhibitory activity of SQDG. SQDG binding to p53 DBD could be reversed with a non-ionic detergent, Nonidet P-40. This is the first study of a glycolipid, SQDG, acting as a dsDNA binding inhibitor of p53, and it could be considered that a SQDG-containing thylakoid membrane in plant chloroplasts might regulate the activity of p53 for cell division, cell cycle checkpoint and tumor suppression.
