The coding properties of the 3 major valine tRNA isoacceptors of
Drosophila melanogaster, the nucleotide sequences of tRNA[sub=Val, sub=3b] and
tRNA[sub=Val, sub=4] and the nucleotide sequences of genes for these two tRNAs have
been determined. Valyl-tRNA[sub=Val, sub=3a] binds strongly to ribosomes in response
to the trinucleotide GUA and to a lesser extent with GUU and GUG. Valyl- tRNA[sub=Val, sub=3b] binds strongly in the presence of GUG and very weakly
with the other 3 triplets whereas valyl- tRNA[sub=Val, sub=4] binds strongly in the
presence of GUU, GUC, and GUA and weakly with GUG.
The nucleotide sequences of tRNA[sub=Val, sub=3b] and tRNA[sub=Val, sub=4] were determined
by a combination of techniques. For both tRNAs most of the sequence was determined by the method of Stanley and Vassilenko. The sequences at the 5' and 3'-ends of the molecules were determined by wandering-spot analysis. Regions of the molecules that could not be sequenced by these two techniques were determined by the gel read-off method. The use of tRNA modified with chloroacetaldehyde to overcome problems in sequencing RNA by the gel read-off method caused by secondary structure in the RNA is
described. The nucleotide sequence of tRNA[sub=Val, sub=4] is: GUUU[sub=m]⁷CCGUm¹GGUG ѱAGCGGDU (acp³ U)AUCACA1ѱCUGCC[sub=m]UIACAm⁵CGCAGAAGm⁷GCCCCCGGѱC Gm¹ AUCCCGGGCGGAAACACCA. About
50% of the U residues at position 20 are modified to acp³U. One of the C
residues at position 48 or 49 is probably modified to m5C. The nucleotide
sequence of tRNA[sub=Val, sub=3b] is: GUUUCCGѱAGUGS1 AGCGGDacp³ UAUCACGѱGUGCUUC ACACGCACAAGm⁷-
GDCCCCGGTѱCGm¹ AACCC GGGCGGGAACACCA. The C residue at position 48 is probably modified to m⁵C. The observed codon responses of the two tRNAs are discussed
in relation to the anticodons found.
Val
The two tRNA[sub=Val, sub=4] genes of the recombinant plasmid pDt55 were sequenced by the Maxam and Gilbert method. This plasmid hybridizes to the
70BC site on the polytene chromosomes, a major site of tRNA[sub=Val, sub=4] hybridization.
The two genes are of opposite polarity and are separated by 525 bp
of DNA. The genes have identical sequences, which correspond to that
expected from the sequence of tRNA[sub=Val, sub=4].
The nucleotide sequence of the tRNA[sub=Val, sub=3b] gene of recombinant
plasmid pDt78R was also determined. This plasmid hybridizes to the 84D
site, a major site of tRNA[sub=Val, sub=3b] hybridization. The sequence of the gene
corresponds to that expected from the sequence of tRNA[sub=Val, sub=3b].
Comparison of the valine tRNA genes sequenced in this study and those
determined by other workers shows that tRNA genes from major sites of
tRNA[sub=Val, sub=3b] or tRNA[sub=Val, sub=4] hybridization to polytene chromosomes correspond exactly to the tRNA[sub=Val] sequences while tRNA tRNA[sub=Val] genes from minor
sites of tRNA hybridization differ at 4 positions from the sequences expected on the basis of the tRNA sequences. The possible significance of this finding is discussed. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/23294 |
| Date | January 1982 |
| Creators | Addison, William Robert |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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