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Applied and Environmental Microbiology, September 2001, p. 4166-4176, Vol. 67, No. 9
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.9.4166-4176.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Role of an Essential Acyl Coenzyme A Carboxylase in the Primary and Secondary Metabolism of Streptomyces coelicolor A3(2)

E. Rodríguez,1 C. Banchio,1 L. Diacovich,1 M. J. Bibb,2 and H. Gramajo1,*

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000-Rosario, Argentina,1 and Department of Molecular Microbiology, John Innes Centre, Colney Lane, Norwich NR4 7UH, United Kingdom2

Received 5 March 2001/Accepted 27 June 2001

Two genes, accB and accE, that form part of the same operon, were cloned from Streptomyces coelicolor A3(2). AccB is homologous to the carboxyl transferase domain of several propionyl coezyme A (CoA) carboxylases and acyl-CoA carboxylases (ACCases) of actinomycete origin, while AccE shows no significant homology to any known protein. Expression of accB and accE in Escherichia coli and subsequent in vitro reconstitution of enzyme activity in the presence of the biotinylated protein AccA1 or AccA2 confirmed that AccB was the carboxyl transferase subunit of an ACCase. The additional presence of AccE considerably enhanced the activity of the enzyme complex, suggesting that this small polypeptide is a functional component of the ACCase. The impossibility of obtaining an accB null mutant and the thiostrepton growth dependency of a tipAp accB conditional mutant confirmed that AccB is essential for S. coelicolor viability. Normal growth phenotype in the absence of the inducer was restored in the conditional mutant by the addition of exogenous long-chain fatty acids in the medium, indicating that the inducer-dependent phenotype was specifically related to a conditional block in fatty acid biosynthesis. Thus, AccB, together with AccA2, which is also an essential protein (E. Rodriguez and H. Gramajo, Microbiology 143:3109-3119, 1999), are the most likely components of an ACCase whose main physiological role is the synthesis of malonyl-CoA, the first committed step of fatty acid synthesis. Although normal growth of the conditional mutant was restored by fatty acids, the cultures did not produce actinorhodin or undecylprodigiosin, suggesting a direct participation of this enzyme complex in the supply of malonyl-CoA for the synthesis of these secondary metabolites.

* Corresponding author. Mailing address: IBR, Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000-Rosario, Argentina. Phone: 54-341-4350661. Fax: 54-341-4390465. E-mail: gramajo{at}infovia.com.ar.

Applied and Environmental Microbiology, September 2001, p. 4166-4176, Vol. 67, No. 9
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.9.4166-4176.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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Copyright © 2001 by the American Society for Microbiology. All rights reserved.