dictyNews Electronic Edition Volume 27, number 2 July 21, 2006 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ============= Abstracts ============= Novel phosphatidylinositol phosphate kinases with G-protein coupled receptor signature are shared by Dictyostelium and Phytophthora Deenadayalan Bakthavatsalam 1,3, *, Harold J.G. Meijer 2, *, Angelika A. Noegel 1 and Francine Govers 2 1 Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty and Centre for Molecular Medicine Cologne, University of Cologne, Cologne, Germany. 2 Laboratory of Phytopathology, Plant Sciences Group, Wageningen University, Binnenhaven 5, NL-6709 PD Wageningen, The Netherlands. 3 Present address: Rice University, Department of Biochemistry and Cell Biology, 6100 S Main Street MS 140, Houston, Texas 77005, USA. * These authors contributed equally to this work. Trends in Microbiology, in press G-protein coupled receptors (GPCR) and phosphatidylinositol phosphate kinases (PIPK) are important key switches in signal transduction pathways. A novel class of proteins was identified in the genomes of two non-related organisms that harbor both a GPCR- and a PIPK-domain. Dictyostelium discoideum contains one GPCR-PIPK which is crucial in cell density sensing. The genomes of Phytophthora sojae and Phytophthora ramorum each encode twelve GPCR-PIPKs. Intriguingly, these are currently the only species that have these two domains combined in one protein. The structural and regulatory characteristics of GPCR-PIPKs are presented and discussed. It is hypothesized that, upon activation, GPCR-PIPKs are capable to trigger heterotrimeric G-protein signaling and phosphoinositide second-messenger synthesis. Submitted by: Deen Bakthavatsalam [deen@rice.edu] ----------------------------------------------------------------------------- Biosynthesis of dictyostelium differentiation inducing factor by a hybrid type I fatty acid-type III polyketide synthase Michael B. Austin1,6, Tamao Saito2,6, Marianne E. Bowman1, Stephen Haydock3, Atsushi Kato2, Bradley S. Moore4, Robert R. Kay5*, and Joseph P. Noel1* 1Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA 2Division of Biological Sciences, Graduate School of Science, Hokkaido University 060-0810 Sapporo, Japan 3Biochemistry Department, University of Cambridge, Cambridge CB2 1QW, UK 4Scripps Institution of Oceanography and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92037-0634, USA 5MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK 6These authors contributed equally to this work. Nature Chemical Biology, in press Differentiation Inducing Factors (DIFs) modulate formation of distinct communal cell types from identical Dictyostelium discoideum amoeba, but DIF biosynthesis remains obscure. We report complimentary in vivo and in vitro experiments identifying one of two ~3000-residue D. discoideum proteins, termed 'steely', as responsible for biosynthesis of the DIF acyl phloroglucinol scaffold. Steely proteins possess six catalytic domains homologous to metazoan type I Fatty Acid Synthases (FASs), but feature an iterative type III Polyketide Synthase (PKS) in place of the expected FAS C-terminal thioesterase (TE) used to off-load fatty acid products. This novel domain arrangement likely facilitates covalent transfer of steely N-terminal acyl products directly to these C-terminal type III PKS active sites, which catalyze both iterative polyketide extension and cyclization. A steely C-terminal domain crystal structure confirms conservation of the homodimeric type III PKS fold. These findings suggest new bioengineering strategies for expanding the scope of fatty acid and polyketide biosynthesis. Submitted by: Richard Gomer [richard@rice.edu] ============================================================================== [End dictyNews, volume 27, number 2]