|Ph.D Thesis||Department of Biology|
|Supervisor:||Prof. Schuster Gadi|
In the chloroplasts, post-transcriptional mechanisms contribute to the regulation of gene expression and they are often mediated by nuclear encoded RNA-binding proteins.
The chloroplast ribosomal protein CS1 is believed to be involved in the process of ribosome binding to mRNA during translation. In order to study initiation complex formation, we studied the RNA-binding properties of the CS1 protein. CS1 protein binds the poly (U) with a high binding affinity. In addition, CS1 binds different RNA molecules, as well as poly (U. These results suggest that the affinity of CS1 for RNA molecules is derived from the number of uridine stretches.
The control of chloroplast mRNA degradation plays a significant role in the regulation of chloroplast gene expression. In order to understand the mechanism of mRNA degradation, the proteins that are involved in that process should be characterized.
In E. coli, PNPase is found in a complex called degradosome. When fractionated on size exclusion column, a recombinant purified PNPase was eluted at 600 kDa. Our results suggest that chloroplast PNPase forms a homo-multimer complex that is not associated with proteins similar to the E. coli degradosome.
Despite of a high homology between the amino acid sequences of E. coli PNPase and spinach PNPase, there is difference in the number of cysteine residues. We suggest that multimeric structure of the chloroplast PNPase and may be its activity as well, are controlled by redox mechanism. To show this we checked the effect of DTT on the PNPase structure and its RNA-binding activity.