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Título

Análisis de las regiones de las proteínas P1 α- y P2 ß que determinan su especificidad estructural y funcional en el tallo ribosómico de Saccharomyces cerevisiae

Autor Briceño, Verónica
DirectorGarcía, Juan Pedro; Santos, Cruz
Palabras clave Saccharomyces cerevisiae
Ribosomas
Análisis de proteínas
Fecha de publicación 2007
EditorUniversidad Autónoma de Madrid
ResumenOne of the most remarkable features of the large ribosomal subunit is the presence of a highly flexible protuberance called the stalk. This protein complex is universally conserved and plays a central role in the ribosome-mediated translation factor activity. However, the organization and functions of the proteins constituting the stalk remain unclear. In bacteria the stalk is made of one copy of protein L10 and two dimers of the acidic protein L7/L12; while in eukaryotes it is composed by P0 (L10 protein-equivalent) and two heterodimers of the acidic proteins P1 and P2. In Saccharomyces cerevisiae, two additional subgroups are distinguished, P1α/P1β and P2α/P2β which form biologically relevant heterodimers, P1α-P2β and P1β-P2α. The fact that in eukaryotes have two different ribosomal families, while in prokaryotes ones have only one, suggest a specialization of functions between both groups. Some data indicate that P1 and P2 proteins have different roles in the assembly and functions of the stalk. However, nowadays the information is very scarce about the possible roles of the two protein types in the stalk function, and some structural features are still unclear. The experiments presented here were designed to explore the different roles that the P1α and P2β proteins may have in the stalk activity, and to characterize more precisely the regions involved in their binding to ribosomes and between them. To fulfil these aims, we designed two series of protein chimeras, comprising consecutively larger and complementary fragments of proteins P1α and P2β, which contained well defined secondary structure elements. These proteins were expressed in yeast strains lacking the corresponding native proteins and the presence of the chimeras in the ribosomes was tested. Similarly, the proteins chimeras were tested using the two-hybrids system to analyze the interactions with the corresponding native proteins. The results allowed us to conclude that the amino acid sequence of the amino-terminal domain that includes the first three α-helices of each protein is the minimal region necessary for binding to the ribosome. The same region is involved in the association of both proteins to form P1α-P2β heterodimers. The data strongly suggest that both processes, heterodimer formation and binding to the ribosome, seem to be necessarily linked. Furthermore, the expression of the chimeras allowed also analyzing the relative importance of the different acidic proteins in the translation and the results show a significant difference in the roles of P1α and P2β proteins.
Descripción Tesis doctoral inédita de la Universidad Autónoma de Madrid, Facultad de Ciencias. Departamento de Biología Molecular. Fecha de lectura: 15-06-2007
URI http://hdl.handle.net/10261/8429
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