OadH from Enterococcus faecalis a novel subunit among the membrane-bound Oxaloacetate decarboxylases

REPIZO, GD; BLANCATO, VS; MAGNI, C

San Miguel de Tucumán

Congreso; XLV Reunión Anual de SAIB; 2009

Sociedad Argentina de Investigación en Bioquímica y Bilogía Molecular

Citrate metabolism in E. faecalis involves the conversion of citrate to pyruvate, by the sequential action of citrate lyase and oxaloacetate decarboxylase (OAD) enzymes. Our previous reports indicated that the gene cluster involved in citrate degradation in E. faecalis encodes an OAD membrane-bound complex homologous to the one present in Klebsiella pneumoniae. In K. pneumoniae the complex is composed of three subunits (Kpn-α, β and γ), while in E. faecalis a four subunit complex was found (Ef-α, β, δ and h). Interestingly, we found that the EfoadH gene encodes a new subunit (Ef-h), which may have functional properties analogous to the Kpn-γ subunit. Analysis of the subunits localization, revealed that those that in principle were soluble (α and δ) were found in the cytoplasm as well as attached to the membrane of E. faecalis, suggesting that α, δ and h subunits form a soluble complex that is able to interact with the membrane-bound β subunit in a dynamic way. In this work, the nature of the interaction between the subunits was analyzed. We observed that the complex was stable at acidic pH suggesting that it´s integrity could be maintained in a different manner than the one reported for Kpn-OAD. Furthermore, different subunits were cloned and expressed in E. coli. In summary, we propose that the new h subunit mediates the interaction between the remaining subunits of the complex.