Affiliation:
1. Department of Biological Sciences, University of Alabama—Huntsville, Huntsville, Alabama 35899
2. Department of Biological Sciences, Stanford University, Stanford, California 94305-5020
Abstract
ABSTRACT
Expression of the
tna
operon of
Escherichia coli
and of
Proteus vulgaris
is induced by
l
-tryptophan. In
E. coli
, tryptophan action is dependent on the presence of several critical residues (underlined) in the newly synthesized TnaC leader peptide,
W
FNI
D
XX
L/I
XXXX
P
. These residues are conserved in TnaC of
P. vulgaris
and of other bacterial species. TnaC of
P. vulgaris
has one additional feature, distinguishing it from TnaC of
E. coli
; it contains two C-terminal lysine residues following the conserved proline residue. In the present study, we investigated
l
-tryptophan induction of the
P. vulgaris tna
operon, transferred on a plasmid into
E. coli
. Induction was shown to be
l
-tryptophan dependent; however, the range of induction was less than that observed for the
E. coli tna
operon. We compared the genetic organization of both operons and predicted similar folding patterns for their respective leader mRNA segments. However, additional analyses revealed that
l
-tryptophan action in the
P. vulgaris tna
operon involves inhibition of TnaC elongation, following addition of proline, rather than inhibition of leader peptide termination. Our findings also establish that the conserved residues in TnaC of
P. vulgaris
are essential for
l
-tryptophan induction, and for inhibition of peptide elongation. TnaC synthesis is thus an excellent model system for studies of regulation of both peptide termination and peptide elongation, and for studies of ribosome recognition of the features of a nascent peptide.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
15 articles.
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