Sat Gene vs SatF Gene in E. coli
Direct Answer
The sat gene encodes the Secreted Autotransporter Toxin (Sat), a well-characterized 107-kDa serine protease virulence factor in pathogenic E. coli strains, while there is no established "satF gene" in the medical literature—you may be referring to a different gene or a nomenclature variation.
The Sat Gene: Function and Clinical Significance
Molecular Characteristics
The sat gene encodes a 142-kDa precursor protein that is processed to a 107-kDa mature toxin belonging to the SPATE (Serine Protease Autotransporters of Enterobacteriaceae) family 1. The protein contains:
- An unusually long 49-amino acid signal sequence
- A 107-kDa passenger domain with a consensus serine protease active site (GDSGSG)
- A 30-kDa C-terminal autotransporter domain for secretion 1
Pathogenic Mechanisms
Sat functions as a cytotoxin that disrupts epithelial cell integrity through multiple mechanisms:
- Cytoskeletal disruption: Sat is internalized into polarized cells and causes F-actin disruption, leading to cell detachment 2
- Tight junction damage: The toxin promotes lesions in tight junctions by inducing rearrangements of ZO-1, ZO-3, and occludin proteins, increasing paracellular permeability in a serine protease-dependent manner 3
- Broad cytopathic activity: Sat exhibits cytotoxic effects on kidney (VERO, LLC-PK1), bladder (HK-2), intestinal (Caco-2), and endothelial (HUVEC) cell lines, with endothelial cells showing the highest sensitivity 2, 1
Clinical Distribution and Significance
The sat gene shows distinct prevalence patterns across different E. coli pathotypes and infection sites:
Urinary Tract Infections
- Highly prevalent in uropathogenic E. coli (UPEC), particularly in Afa/Dr diffusely adhering E. coli (DAEC) strains causing UTI (88% positive) 3
- Significantly more common in strains from acute pyelonephritis compared to fecal commensal strains 1
Intestinal Infections
- Strong correlation with diffusely adhering E. coli (DAEC) in intestinal isolates (44% prevalence) 4
- Present in 93.7% of enteroaggregative E. coli (EAEC) strains harboring the gene 2
- Found in approximately 46% of DAEC strains from children with diarrhea, but only 16% from children without diarrhea 3
Invasive Infections
- Detected in E. coli strains isolated from neonatal septicemia and meningitis 2
- The intense activity on endothelial cells suggests Sat may function as a virulence factor during bacteremia 2
Immunogenicity
Sat elicits a strong antibody response during infection, as demonstrated in mice infected with E. coli CFT073, supporting its role as an active virulence determinant rather than a passive bystander 1.
Important Clinical Caveat
There is no established "satF gene" in the E. coli literature based on the available evidence. If you are asking about a related gene, consider:
- Other SPATE family members: PicU is another serine protease autotransporter identified in UPEC that is homologous to Pic protein from Shigella flexneri 5
- Nomenclature variations: Confirm the exact gene designation, as bacterial gene nomenclature can vary between databases and publications
If you have additional context about "satF," please clarify the source or provide the specific pathotype or strain in question for more targeted information.