Ribosomens basala mekanismer
Tidsperiod: 2013-01-01 till 2015-12-31
Projektledare: Måns Ehrenberg
Budget: 4 200 000 SEK
The ribosome is a large macromolecular complex of two subunits. It links amino acids into proteins according to the messenger RNA (mRNA) instructions. The twenty amino acids (aa) are covalently coupled to their cognate transfer RNAs (tRNAs) and brought to the mRNA-bound ribosome as aa-tRNAs in ternary complex with elongation factor Tu (EF-Tu) and GTP. When the anticodon base triplet of a tRNA matches the codon triplet of an mRNA, GTP is hydrolyzed on EF-Tu, which then dissociates from the ribosome. The aa-tRNA accommodates in the A site of the ribosome and receives the nascent peptide from the P-site tRNA. We will study the accuracy by which the ribosome accepts aa-tRNAs with anticodons matching the mRNA codons and rejects other tRNAs. We have found a linear trade-off between the rate of aa-tRNA acceptance and the accuracy of aa-tRNA selection, which makes it possible to estimate the maximal possible accuracy of tRNA selection and how much of it is currently used. We will also study how tRNA modifications, mutations and antibiotics affect the maximal and current accuracy of mRNA translation. We will study the steps in which the mRNA is moved in the ribosomal reading frame, and in which the ribosome is split into subunits and recycled to a new round of initiation. Both these steps are energy driven, involve large structural changes of the ribosome and are poorly understood. We will use our biochemical data of protein synthesis as input for global models of bacterial growth.