dictyNews Volume 27 Number 02

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Dicty News

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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. 

 
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  Abstracts 
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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] 
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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] 
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[End dictyNews, volume 27, number 2]