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J. Bacteriol., May 1995, 2315-2320, Vol 177, No. 9
L Seligman, J Bailey and C Manoil
The Escherichia coli serine chemoreceptor (Tsr) is a protein with a simple
topology consisting of two membrane-spanning sequences (TM1 and TM2)
separating a large periplasmic domain from N-terminal and C- terminal
cytoplasmic regions. We analyzed the contributions of several sequence
elements to the cytoplasmic localization of the C-terminal domain by using
chemoreceptor-alkaline phosphatase gene fusions. The principal findings
were as follows. (i) The cytoplasmic localization of the C-terminal domain
depended on TM2 but was quite tolerant of mutations partially deleting or
introducing charged residues into the sequence. (ii) The basal level of
C-terminal domain export was significantly higher in proteins with the
wild-type periplasmic domain than in derivatives with a shortened
periplasmic domain, suggesting that the large size of the wild-type domain
promotes partial membrane misinsertion. (iii) The membrane insertion of
deletion derivatives with a single spanning segment (TM1 or TM2) could be
controlled by either an adjacent positively charged sequence or an adjacent
amphipathic sequence. The results provide evidence that the generation of
the Tsr membrane topology is an overdetermined process directed by an
interplay of sequences promoting and opposing establishment of the normal
structure.
Copyright © 1995, American Society for Microbiology
Sequences determining the cytoplasmic localization of a chemoreceptor domain
Department of Genetics, University of Washington, Seattle 98195, USA.
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