One of three transmembrane stretches is sufficient for the functioning of the SecE protein, a membrane component of the E. coli secretion machinery.
The E. coli secE (prlG) gene codes for an integral cytoplasmic membrane protein which is part of the cell's secretory machinery. A deletion of nearly the entire gene renders the cell dependent on the presence of a complementing secE+ plasmid, indicating that the SecE protein is essential for growth. Deletions which remove carboxy-terminal sequences or substantial amounts near the amino-terminus of SecE can still complement the lethal deletion. This deletion analysis suggests that the essential domain of the SecE protein includes only a single one of its three hydrophobic membrane-spanning segments. Two of three dominant prlG signal sequence suppressors map to this segment. Consistent with the insensitivity of SecE to major structural changes, several cold-sensitive mutations cause lethality not because of any change in the protein, but because of a reduction in its level of expression. Our results suggest that higher levels of the protein are needed at the lower temperature. These findings are discussed in terms of the interactions between various components of the secretory machinery.
Schatz
P J
PJ
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115.
Bieker
K L
KL
Ottemann
K M
KM
Silhavy
T J
TJ
Beckwith
J
J
D000483:Alleles; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002872:Chromosome Deletion; D003080:Cold Temperature; D004269:DNA, Bacterial / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010957:Plasmids; D021382:Protein Sorting Signals / Q000235:genetics; D000069816:SEC Translocation Channels; D013489:Suppression, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli