A PROCEDURE FOR THE PURIFICATION OF BETA-LACTOGLOBULIN FROM BOVINE MILK USING GEL FILTRATION CHROMATOGRAPHY AT LOW pH

A simple and rapid procedure for the purification of beta-lactoglobulin (β-LG) from bovine milk is described. The procedure exploits the major difference in molecular mass of β-LG and other whey components and the existence of the former in monomeric form at acidic pH. Gel filtration of whey was carried out using a Bio-Gel P10 column at pH 3.0. Residual caseins and other milk proteins were excluded from the gel and β-LG and alpha-lactalbumin (α-LA) emerged as two fully resolved peaks. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) suggested that β-LG was purified to apparent homogeneity, while absorption, fluorescence, and circular dichroism spectroscopy indicated the native-like conformation of the protein. Western blot analysis revealed that the antibodies raised against the purified β-LG in rabbits also readily react with the commercial bovine protein. This procedure requires only 4–5 hr for the purification of about 10 mg of β-LG from a single run while using a small column (2.3 cm × 83 cm) of Bio-Gel P10 and has the potential for scaling up.     

Identification and distribution of a GABA receptor mutation conferring dieldrin resistance in the malaria vector Anopheles funestus in Africa

Growing problems of pyrethroid resistance in Anopheles funestus have intensified efforts to identify alternative insecticides. Many agrochemicals target the GABA receptors, but cross-resistance from dieldrin resistance may preclude their introduction.Dieldrin resistance was detected in An. funestus populations from West (Burkina Faso) and central (Cameroon) Africa, but populations from East (Uganda) and Southern Africa (Mozambique and Malawi) were fully susceptible to this insecticide. Partial sequencing of the dieldrin target site, the ??-aminobutyric acid (GABA) receptor, identified two amino acid substitutions, A296S and V327I. The A296S mutation has been associated with dieldrin resistance in other species. The V327I mutations was detected in the resistant sample from Burkina Faso and Cameroon and consistently associated with the A296S substitution. The full-length of the An. funestus GABA-receptor gene, amplified by RT-PCR, generated a sequence of 1674 bp encoding 557 amino acid of the protein in An. funestus with 98% similarity to that of Anopheles gambiae. Two diagnostic assays were developed to genotype the A296S mutation (pyrosequencing and PCR-RFLP), and use of these assays revealed high frequency of the resistant allele in Burkina Faso (60%) and Cameroon (82%), moderate level in Benin (16%) while low frequency or absence of the mutation was observed respectively in Uganda (7.5%) or 0% in Malawi and Mozambique.The distribution of the Rdl^R mutation in An. funestus populations in Africa suggests extensive barriers to gene flow between populations from different regions.     

Crystal structures of a family 8 polysaccharide lyase reveal open and highly occluded substrate-binding cleft conformations

Bacterial enzymatic degradation of glycosaminoglycans such as hyaluronan and chondroitin is facilitated by polysaccharide lyases. Family 8 polysaccharide lyase (PL8) enzymes contain at least two domains: one predominantly composed of α-helices, the α-domain, and another predominantly composed of β-sheets, the β-domain. Simulation flexibility analyses indicate that processive exolytic cleavage of hyaluronan, by PL8 hyaluronate lyases, is likely to involve an interdomain shift, resulting in the opening/closing of the substrate-binding cleft between the α- and β-domains, facilitating substrate translocation. Here, the Streptomyces coelicolor A3(2) PL8 enzyme was recombinantly expressed in and purified from Escherichia coli and biochemically characterized as a hyaluronate lyase. By using X-ray crystallography its structure was solved in complex with hyaluronan and chondroitin disaccharides. These findings show key catalytic interactions made by the different substrates, and on comparison with all other PL8 structures reveals that the substrate-binding cleft of the S. coelicolor enzyme is highly occluded. A third structure of the enzyme, harboring a mutation of the catalytic tyrosine, created via site-directed mutagenesis, interestingly revealed an interdomain shift that resulted in the opening of the substrate-binding cleft. These results add further support to the proposed processive mechanism of action of PL8 hyaluronate lyases and may indicate that the mechanism of action is likely to be universally used by PL8 hyaluronate lyases.     

Functional analysis of novel sulfotransferases in the silkworm Bombyx mori

Sulfoconjugation plays a vital role in the detoxification of xenobiotics and in the metabolism of endogenous compounds. In this study, we aimed to identify new members of the sulfotransferase (SULT) superfamily in the silkworm Bombyx mori. Based on amino acid sequence and phylogenetic analyses, two new enzymes, swSULT ST1 and swSULT ST2, were identified that appear to belong to a distinct group of SULTs including several other insect SULTs. We expressed, purified, and characterized recombinant SULTs. While swSULT ST1 sulfated xanthurenic acid and pentachlorophenol, swSULT ST2 exclusively utilized xanthurenic acid as a substrate. Based on these results, and those concerning the tissue distribution and substrate specificity toward pentachlorophenol analyses, we hypothesize that swSULT ST1 plays a role in the detoxification of xenobiotics, including insecticides, in the silkworm midgut and in the induction of gametogenesis in silkworm ovary and testis. Collectively, the data obtained herein contribute to a better understanding of SULT enzymatic functions in insects.     

Identification of embryonic lethal genes in humans by autozygosity mapping and exome sequencing in consanguineous families

BackgroundIdentifying genetic variants that lead to discernible phenotypes is the core of Mendelian genetics. An approach that considers embryonic lethality as a bona fide Mendelian phenotype has the potential to reveal novel genetic causes, which will further our understanding of early human development at a molecular level. Consanguineous families in which embryonic lethality segregates as a recessive Mendelian phenotype offer a unique opportunity for high throughput novel gene discovery as has been established for other recessive postnatal phenotypes.ResultsWe have studied 24 eligible families using autozygosity mapping and whole-exome sequencing. In addition to revealing mutations in genes previously linked to embryonic lethality in severe cases, our approach revealed seven novel candidate genes (THSD1, PIGC, UBN1, MYOM1, DNAH14, GALNT14, and FZD6). A founder mutation in one of these genes, THSD1, which has been linked to vascular permeability, accounted for embryonic lethality in three of the study families. Unlike the other six candidate genes, we were able to identify a second mutation in THSD1 in a family with a less severe phenotype consisting of hydrops fetalis and persistent postnatal edema, which provides further support for the proposed link between this gene and embryonic lethality.ConclusionsOur study represents an important step towards the systematic analysis of “embryonic lethal genes” in humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-015-0681-6) contains supplementary material, which is available to authorized users.     

Degron mediated BRM/SMARCA2 depletion uncovers novel combination partners for treatment of BRG1/SMARCA4-mutant cancers

Recent studies have highlighted that cancer cells with a loss of the SWI/SNF complex catalytic subunit BRG1 are dependent on the remaining ATPase, BRM, making it an attractive target for cancer therapy. However, an understanding of the extent of target inhibition required to arrest cell growth, necessary to develop an appropriate therapeutic strategy, remains unknown. Here, we utilize tunable depletion of endogenous BRM using the SMASh degron, and interestingly observe that BRG1-mutant lung cancer cells require near complete depletion of BRM to robustly inhibit growth both in vitro and in vivo. Therefore, to identify pathways that synergize with partial BRM depletion and afford a deeper response, we performed a genome-wide CRISPR screen and discovered a combinatorial effect between BRM depletion and the knockout of various genes of the oxidative phosphorylation pathway and the anti-apoptotic gene MCL1. Together these studies provide an important framework to elucidate the requirements of BRM inhibition in the BRG1-mutant state with implications on the feasibility of targeting BRM alone, as well as reveal novel insights into pathways that can be exploited in combination toward deeper anti-tumor responses.     

Ruthenium complexes of furan- and thiophene-thiolates: Structure of CpRu(dppe)SThi

Complexes of ruthenium containing 2-furan- and 2-thiophene-thiolates with phosphine ligands have been prepared and characterized. The bis(triphenylphosphine) complexes CpRu(PPh₃)₂SR (R = C₄H₃O: Fu (1a), C₄H₃S: Thi (1b)) were prepared by the reaction of thiolato anions (FuS^? or ThiS^?) with CpRu(PPh₃)₂Cl. The one-pot reaction of CpRu(PPh₃)₂Cl, thiolato anions and L ligands gave CpRu(L)SR (L = bis(diphenylphosphino)methane: dppm (2); bis(diphenylphosphino)ethane: dppe (3)). The newly prepared complexes have been characterized by spectroscopic techniques (FT-IR, ¹H NMR and ³¹P NMR) and by elemental analysis. The crystal structure of CpRu(dppe)SThi (3b) has been determined by X-ray diffraction.