Date of Award


Document Type


Degree Name

Master of Science (MS)


Chemistry & Biochemistry



Committee Director

T. O. Sitz

Committee Member

James Yuan

Committee Member

Roscoe O. Carter

Committee Member

Frank E. Scully, Jr.

Call Number for Print

Special Collections LD4331.C45 B35


5.8S rRNA is a low molecular weight ribosomal RNA which is noncovalently bonded to the larger ribosomal subunit 28S rRNA; through its 3' end and through its 5' end. This interaction is an integral part of the ribosome, and plays an important role in the ribosome structure and function.

There is a high degree of homology between the 5.8S rRNA primary structures of rat, turtle and chicken. The base sequence of rat 5.8S rRNA differs only in one position from that of turtle and in three positions that of cl1.icken. Tl1ere is a single purine substitution at the 5' end in the case of turtle and chicken and a pyrimidine substitution along with an extra pyrim~dine on the 3' end in case of chicken with respect to rat 5.8S rRNA sequence. It was determined that the thermal stability of tat 5.8S-28S rRNA complex in 0.15 M salt was about 3°C to 4°C lower than that of turtle or chicken, whereas turtle and chicken complex have the same stabilities. This suggested that the adenylic acid residue situated on the 5' end of the 5.8S rRNA from chicken and turtle plays an important role in binding them to their respective 28S species, whereas in 5.8S sequence for rat this adenylic acid has been changed ~ to a guanylic acid and probably is unable to pair strongly with

the corresponding base in its 28S sequence, thus reducing the stability of the 5.8S-28S complex from rat. This could be explained by sequence changes in the 28S. To examine this possibility, the stabilities of heterologous complexes were determined. Since the guanylic acid residue in rat 5.8S is situated at the 5' end of the 5.8S molecule and is probably the cause of the diminished stability of either the homologous or heterologous complexes, this clearly shows that the 5' end also plays a very important role in binding to the 28S species. However, the stabilities of the heterologous complexes were dependent only on the 5.8S rRNAs used demonstrating identical binding sites in 28S RNA from the three species.


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