Evolution of mitochondrial tRNAs

1. N. A. Zaytseva1, F. A. Kondrashov2, P. K. Vlasov2 1Siberian Federal University, Krasnoyarsk, Russia 2Centre for Genomic Regulation, Barcelona, Spain Evolution of mitochondrial tRNAs

2. Introduction • The global tRNA evolution within the total sequence space has not been explored. • The lack of data on the distribution and evolution of the sequences makes a significant gap in our understanding of evolution of amino acids and genetic code.

3. Goal and Tasks • Goal Demonstration of transition possibility one group tRNA to another • Tasks 1) To obtain a picture of groups tRNA distribution 2) To assess the divergence of sequences within each group of tRNA

4. Expanding protein universe • The analysis is based on the model of the ongoing expansion of the protein universe.

5. Expanding protein universe • The rate of divergence of distant homologues is analogous to speed in Hubble’s analysis; the distance between sequences is analogous to physical distance.

6. Databases and methods • 5787 sequences of mitochondrial tRNAs (Tetrapoda) were analyzed • The sequences were retrieved from http://www.umich.edu/~kondrash/Database/ • The general database (Tetrapoda) was divided into four databases: Mammalia, Aves, Amphibia and Reptilia

7. Databases and methods • Step 1. The consensus sequences for each group of tRNA were determined. • Step 2. The values of effective radius were computed. • Step 3. The distances from all the sequences to each consensus were calculated. • Step 4. The sequences, which are located in the effective radius of another groups, were identified.

8. tRNAs of histidine, isoleucine,leucineand tyrosine make a cluster • Picture 1— Reduced version of intersection matrix (Tetrapoda).

9. Formation of cluster isn’t related to values of effective radius Table 1 — Values of effective radius for some tRNA groups.

10. Size of effective radius doesn’t depend on databases size • Table 2— Average value of effective radius for each database. • Table 3— Number of tRNA sequences in each database.

11. The value of effective radius depends on the origin time of species included into database Picture 2— Correlation between effective radius and origin time of group.

12. The effective radius is independent on the chronology of amino acids origin Picture 3— Correlation between value of effective radius and chronology of amino acids origin.

13. Conclusion • Histidine, isoleucine, lecine and tyrosine form cluster. In the center of cluster the tyrosine group is located. • There is a correlation between the effective radius and origin time of group of species taken into consideration. • The value of the effective radius is independent on the chronology of amino acids origin.

14. Perspectives • When the investigation is finished,we will have a better understanding of the nature of tRNA distribution in sequence space.

15. Acknowledgment Fyodor Kondrashov Peter Vlasov Michael Sadovsky This work was supported by grant from Russian government department of Science and Education to Siberian Federal University «The genetic researcher of the Siberian larch»