INVESTIGADORES
GRAMAJO Hugo Cesar
artículos
Título:
Crystal Structure of the Beta Subunit of Acyl-CoA Carboxylase: Structure Based Engineering of Substrate Specificity
Autor/es:
LAUTARO DIACOVICH, DEBORAH MITCHELL, HUY PHAM, GABRIELA GAGO, MELROSE MELGAR, CHAITAN KHOSLA, HUGO GRAMAJO, SHIOU-CHUAN TSAI
Revista:
BIOCHEMISTRY
Referencias:
Año: 2004 p. 14027 - 14036
ISSN:
0006-2960
Resumen:
Acetyl-CoA carboxylase (ACC) and propionyl-CoA carboxylase (PCC)
catalyze the carboxylation of acetyl- and propionyl-CoA to generate
malonyl- and methylmalonyl-CoA, respectively. Understanding the
substrate specificity of ACC and PCC will (1) help in the development
of novel structure-based inhibitors that are potential therapeutics
against obesity, cancer, and infectious disease and (2) facilitate
bioengineering to provide novel extender units for polyketide
biosynthesis. ACC and PCC in Streptomyces coelicolor are multisubunit
complexes. The core catalytic beta-subunits, PccB and AccB, are 360 kDa
homohexamers, catalyzing the transcarboxylation between biotin and
acyl-CoAs. Apo and substrate-bound crystal structures of PccB hexamers
were determined to 2.0-2.8 A. The hexamer assembly forms a ring-shaped
complex. The hydrophobic, highly conserved biotin-binding pocket was
identified for the first time. Biotin and propionyl-CoA bind
perpendicular to each other in the active site, where two oxyanion
holes were identified. N1 of biotin is proposed to be the active site
base. Structure-based mutagenesis at a single residue of PccB and AccB
allowed interconversion of the substrate specificity of ACC and PCC.
The di-domain, dimeric interaction is crucial for enzyme catalysis,
stability, and substrate specificity; these features are also highly
conserved among biotin-dependent carboxyltransferases. Our findings
enable bioengineering of the acyl-CoA carboxylase (ACCase) substrate
specificity to provide novel extender units for the combinatorial
biosynthesis of polyketides.