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Characterization of the AGPase large subunit isoforms from tomato indicates that the recombinant L3 subunit is active as a monomer.
Petreikov, Marina; Eisenstein, Miriam; Yeselson, Yelena; Preiss, Jack; Schaffer, Arthur A.
Afiliação
  • Petreikov M; Department of Vegetable Research, Volcani Center-ARO, Bet Dagan 50250, Israel.
Biochem J ; 428(2): 201-12, 2010 May 13.
Article em En | MEDLINE | ID: mdl-20236089
The enzyme AGPase [ADP-Glc (glucose) pyrophosphorylase] catalyses a rate-limiting step in starch synthesis in tomato (Solanum lycopersicon) fruit, which undergoes a transient period of starch accumulation. It has been a generally accepted paradigm in starch metabolism that the enzyme naturally functions primarily as a heterotetramer comprised of two large subunits (L) and two small subunits (S). The tomato genome harbours a single gene encoding S and three genes for L proteins, which are expressed in both a tissue- and time-specific manner. In the present study the allosteric contributions of the different L subunits were compared by expressing each one in Escherichia coli, in conjunction with S and individually, and characterizing the resulting enzyme activity. Our results indicate different kinetic characteristics of the tomato L1/S and L3/S heterotetramers. Surprisingly, the recombinant L3 protein was also active when expressed alone and size-exclusion and immunoblotting showed that it functioned as a monomer. Subunit interaction modelling pointed to two amino acids potentially affecting subunit interactions. However, directed mutations did not have an impact on subunit tetramerization. These results indicate a hitherto unknown active role for the L subunit in the synthesis of ADP-Glc.
Assuntos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Proteínas de Plantas / Proteínas Recombinantes / Solanum lycopersicum / Isoformas de Proteínas / Subunidades Proteicas / Glucose-1-Fosfato Adenililtransferase Tipo de estudo: Prognostic_studies Idioma: En Revista: Biochem J Ano de publicação: 2010 Tipo de documento: Article País de afiliação: Israel

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Proteínas de Plantas / Proteínas Recombinantes / Solanum lycopersicum / Isoformas de Proteínas / Subunidades Proteicas / Glucose-1-Fosfato Adenililtransferase Tipo de estudo: Prognostic_studies Idioma: En Revista: Biochem J Ano de publicação: 2010 Tipo de documento: Article País de afiliação: Israel