Self-associating autotransporters, SAATs: Functional and structural similarities

• Published in: International journal of medical microbiology 2006-08, Vol.296 (4), p.187-195
• Main Authors: Klemm, Per, Vejborg, Rebecca Munk, Sherlock, Orla
• Format: Article
• Language: English
• Subjects: Adhesins, Bacterial - chemistry; Adhesins, Bacterial - genetics; Adhesins, Bacterial - metabolism; Adhesins, Escherichia coli - chemistry; Adhesins, Escherichia coli - genetics; Adhesins, Escherichia coli - metabolism; Ag43; AIDA; Autotransporter; Bacterial Adhesion; Bacterial aggregation; Bacterial Capsules - physiology; Bacterial Outer Membrane Proteins - chemistry; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Biofilm; Biofilms - growth & development; Biological Transport; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Escherichia coli; Escherichia coli - physiology; Fimbriae, Bacterial - physiology; Gram-Negative Bacteria - physiology; Hydrogen-Ion Concentration; TibA
• ISSN: 1438-4221; 1618-0607
• DOI: 10.1016/j.ijmm.2005.10.002

The autotransporter family of translocated proteins in Gram-negative bacteria all contain three structural motifs, a signal sequence, a passenger domain and a translocator domain. The autotransporters constitute a highly versatile group of proteins with respect to function, which accords with the widespread presence of these proteins. The group encompasses many important virulence factors. In Escherichia coli, a subgroup of autotransporter proteins consists of the TibA adhesin/invasin associated with some enterotoxigenic E. coli, the AIDA adhesin from diarrhea-causing E. coli and finally, the Ag43 autoaggregation factor found in the majority of E. coli strains. The three proteins exhibit ∼25% identity at the sequence level, and are quite different with respect to size, glycosylation and processing. Nevertheless, they share some important properties: all are self-associating proteins that cause bacterial aggregation. They can also interact with each other via heterologous interactions to cause formation of mixed bacterial aggregates. Furthermore, these proteins enhance biofilm formation. Based on these properties we propose to classify them together in a group termed SAATs: self-associating autotransporters.