Volume 270,
Number 26,
Issue of June 30, pp. 15908-15914, 1995
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
Maturation
of Pre-tRNA
by Escherichia coli RNase P Is
Specified by a Guanosine of the 5`-Flanking Sequence
Thierry
Meinnel
,
Sylvain
Blanquet
The C
/A
base pair at the
top of the acceptor stem of Escherichia coli tRNA
accounts for several of the specialized roles of this tRNA in
translation initiation. According to the rules of RNA substrate
recognition by RNase P, the C
/A
pair is likely to disfavor the 5`-maturation of
pre-tRNA
. Indeed, in contrast to other E. coli tRNA species, tRNA
was not properly matured when
overproduced from a multicopy expression vector. Half of the recovered
tRNA
retained an extension at the 5` side. Such a defect
of tRNA
processing could be cured by changing bases
C
and A
by a Watson-Crick base
pair or by non-paired bases, provided one of them was a G. It could
also be compensated by either (i) overexpression of RNase P or (ii)
introduction within the plasmid of one out of the three 5`-flanking
sequences naturally occurring in the four E. coli tRNA
genes. The effect of these flanking sequences
on the maturation of tRNA
could be accounted for by the
presence of a G located 2 bases upstream from C
.
Notably, this G is the only residue that is conserved in the
5`-flanking sequences of all four E. coli tRNA
genes.