The transmembrane helix of the Escherichia coli division protein FtsI localizes to the septal ring.
FtsI (also called PBP3) of Escherichia coli is a transpeptidase required for synthesis of peptidoglycan in the division septum and is one of about a dozen division proteins that localize to the septal ring. FtsI comprises a short amino-terminal cytoplasmic domain, a single transmembrane helix (TMH), and a large periplasmic domain that encodes the catalytic (transpeptidase) activity. We show here that a 26-amino-acid fragment of FtsI is sufficient to direct green fluorescent protein to the septal ring in cells depleted of wild-type FtsI. This fragment extends from W22 to V47 and corresponds to the TMH. This is a remarkable finding because it is unusual [corrected] for a TMH to target a protein to a site more specific than the membrane. Alanine-scanning mutagenesis of the TMH identified several residues important for septal localization. These residues cluster on one side of an alpha-helix, which we propose interacts directly with another division protein to recruit FtsI to the septal ring.
Wissel
Mark C
MC
Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA.
Wendt
Jennifer L
JL
Mitchell
Calista J
CJ
Weiss
David S
DS
D000595:Amino Acid Sequence; D003593:Cytoplasm / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D046915:Penicillin-Binding Proteins / Q000737:chemistry*; D046928:Peptidoglycan Glycosyltransferase / Q000737:chemistry*; D019897:Periplasm / Q000737:chemistry; D017433:Protein Structure, Secondary
D029968:Escherichia coli Proteins; C478704:FtsI protein, E coli; D046915:Penicillin-Binding Proteins; D046928:Peptidoglycan Glycosyltransferase