IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Structural and functional analysis of adaptor proteins of the plant proteolytic Clp system
Autor/es:
COLOMBO, CLARA V.; ROSANO, GERMÁN L; CECCARELLI, EDUARDO A
Lugar:
Puerto Madryn, Argentina
Reunión:
Congreso; XLVI Reunión Anual SAIB; 2010
Institución organizadora:
Sociedad Argentina de Investigación en Bioquímica y Biología Molecular
Resumen:
In chloroplasts, proteome homeostasis is regulated by a network of proteases, molecular chaperones and regulatory proteins. In particular, the tetradecameric Clp proteolytic complex, in assistance with Hsp100 chaperones, selects, disaggregates and unfolds proteins, which can then be re-folded or directed to proteolytic degradation. Little is known about the function of the Clp proteasome. In Escherichia coli, the protein ClpS associates with the bacterial Clp complex and modulates its proteolytic activity. In Arabidopsis thaliana, three proteins (ClpT1/2 and ClpS) were proposed to play this role. We characterized these proteins in vitro and studied their interaction with Hsp100 chaperones. All proteins were expressed in recombinant E. coli cells and purified to homogeneity. Since Clp proteins are usually oligomeric, we analyzed their assembly status by size exclusion chromatography. ClpT1 is a monomeric protein in the absence or presence of 5 mM ATP. Circular dichroism spectroscopy indicates that the protein is properly folded and that its thermal stability is rather low, with an unfolding transition at 45 ºC. ClpT1 stimulates the ATPase activity of the Hsp100 proteins ClpC2 and ClpD. Our results represent the first evidence of the regulatory function of ClpT1 on Hsp100 chaperones and will contribute to elucidate the poorly known regulatory system of the Clp complex from plants.