Functional dissection of a cell-division inhibitor, SulA, of Escherichia coli and its negative regulation by Lon.
SulA is induced in Escherichia coli by the SOS response and inhibits cell division through interaction with FtsZ. To determine which region of SulA is essential for the inhibition of cell division, we constructed a series of N-terminal and C-terminal deletions of SulA and a series of alanine substitution mutants. Arginine at position 62, leucine at 67, tryptophan at 77 and lysine at 87, in the central region of SulA, were all essential for the inhibitory activity. Residues 3-27 and the C-terminal 21 residues were dispensable for the activity. The mutant protein lacking N-terminal residues 3-47 was inactive, as was that lacking the C-terminal 34 residues. C-terminal deletions of 8 and 21 residues increased the growth-inhibiting activity in lon+ cells, but not in lon- cells. The wild-type and mutant SulA proteins were isolated in a form fused to E. coli maltose-binding protein, and tested in vitro for sensitivity to Lon protease. Lon degraded wild-type SulA and a deletion mutant lacking the N-terminal 93 amino acids, but did not degrade the derivative lacking 21 residues at the C-terminus. Furthermore, the wild-type SulA and the N-terminal deletion mutant formed a stable complex with Lon, while the C-terminal deletion did not. MBP fused to the C-terminal 20 residues of SulA formed a stable complex with, but was not degraded by Lon. When LacZ protein was fused at its C-terminus to 8 or 20 amin acid residues from the C-terminal region of SulA the protein was stable in lon+ cells. These results indicate that the C-terminal 20 residues of SulA permit recognition by, and complex formation with, Lon, and are necessary, but not sufficient, for degradation by Lon.
Higashitani
A
A
Division of Microbial Genetics, National Institute of Genetics, Mishima, Japan.
Ishii
Y
Y
Kato
Y
Y
Koriuchi
K
K
D018528:ATP-Binding Cassette Transporters; D049069:ATP-Dependent Proteases; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics; D002455:Cell Division; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D004926:Escherichia coli / Q000737:chemistry / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D016296:Mutagenesis; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D049070:Protease La; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013014:SOS Response, Genetics; D017384:Sequence Deletion; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C461599:maltose transport system, E coli; C053139:sulA protein, E coli; D001616:beta-Galactosidase; D049069:ATP-Dependent Proteases; D012697:Serine Endopeptidases; C483567:Lon protein, E coli; D049070:Protease La