Suchergebnisse

BACKGROUND: Many valuable biopharmaceutical and biotechnological proteins have been produced in Escherichia coli, however these proteins are almost exclusively localised in the cytoplasm or periplasm. This presents challenges for purification, i.e. the removal of contaminating cellular constituents. One solution is secretion directly into the surrounding media, which we achieved via the 'hijack' of the flagellar type III secretion system (FT3SS). Ordinarily flagellar subunits are exported through the centre of the growing flagellum, before assembly at the tip. However, we exploit the fact that in the absence of certain flagellar components (e.g. cap proteins), monomeric flagellar proteins are secreted into the supernatant. RESULTS: We report the creation and iterative improvement of an E. coli strain, by means of a modified FT3SS and a modular plasmid system, for secretion of exemplar proteins. We show that removal of the flagellin and HAP proteins (FliC and FlgKL) resulted in an optimal prototype. We next developed a high-throughput enzymatic secretion assay based on cutinase. This indicated that removal of the flagellar motor proteins, motAB (to reduce metabolic burden) and protein degradation machinery, clpX (to boost FT3SS levels intracellularly), result in high capacity secretion. We also show that a secretion construct comprising the 5'UTR and first 47 amino acidsof FliC from E. coli (but no 3'UTR) achieved the highest levels of secretion. Upon combination, we show a 24-fold improvement in secretion of a heterologous (cutinase) enzyme over the original strain. This improved strain could export a range of pharmaceutically relevant heterologous proteins [hGH, TrxA, ScFv (CH2)], achieving secreted yields of up to 0.29 mg L-1, in low cell density culture. CONCLUSIONS: We have engineered an E. coli which secretes a range of recombinant proteins, through the FT3SS, to the extracellular media. With further developments, including cell culture process strategies, we envision further improvement to the secreted titre of recombinant protein, with the potential application for protein production for biotechnological purposes. ; CAG was funded by a University of Sheffield Ph.D. scholarship, NK by a Ph.D. scholarship from the Government of India, and EC by a BBSRC CBMNet Business Innovation voucher to GS and CL. MH was funded by BBSRC Grant to GS and PCW (BB/J016322/1). OJB was funded by a John Lucas Walker studentship awarded by the Department of Pathology, University

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field. ; Common sequence variants have recently joined rare structural polymorphisms as genetic factors with strong evidence for association with schizophrenia. Here we extend our previous genome-wide association study and meta-analysis (totalling 7 946 cases and 19 036 controls) by examining an expanded set of variants using an enlarged follow-up sample (up to 10 260 cases and 23 500 controls). In addition to previously reported alleles in the major histocompatibility complex region, near neurogranin (NRGN) and in an intron of transcription factor 4 (TCF4), we find two novel variants showing genome-wide significant association: rs2312147[C], upstream of vaccinia-related kinase 2 (VRK2) [odds ratio (OR) = 1.09, P = 1.9 × 10(-9)] and rs4309482[A], between coiled-coiled domain containing 68 (CCDC68) and TCF4, about 400 kb from the previously described risk allele, but not accounted for by its association (OR = 1.09, P = 7.8 × 10(-9)). ; European Union LSHM-CT-2006-037761 PIAP-GA-2008-218251 HEALTH-F2-2009-223423 National Genome Research Network of the German Federal Ministry of Education and Research (BMBF) 01GS08144 01GS08147 National Institute of Mental Health R01 MH078075 N01 MH900001 MH074027 Centre of Excellence for Complex Disease Genetics of the Academy of Finland 213506 129680 Biocentrum Helsinki Foundation Faculty of Medicine, University of Helsinki Stanley Medical Research Institute Danish Council for Strategic Research 2101-07-0059 H. Lundbeck A/S Research Council of Norway 163070/V50 South-East Norway Health Authority 2004-123 Medical Research Council Ministerio de Sanidad y Consumo, Spain PI081522 Xunta de Galicia 08CSA005208PR Swedish Research Council Wellcome Trust 083948/Z/07/Z Max Planck Society Eli Lilly and Company ; info:eu-repo/grantAgreement/EC/FP7/218251