Trimeric Autotransporter Adhesins (TAA)

YadA bacterial adhesin anchor domain
The beta barrel structure found in the C-terminus of the bacterial adhesin anchor domain, YadA
Identifiers
Symbol	YadA_anchor
Pfam	PF03895
Pfam clan	CL0327
InterPro	IPR005594
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

YadA head domain
Crystal structure of the collagen-binding domain of Yersinia adhesin YadA
Identifiers
Symbol	YadA_head
Pfam	PF05658
InterPro	IPR008640
SCOP	1p9h
SUPERFAMILY	1p9h
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

In molecular biology, trimeric autotransporter adhesins (TAAs), are proteins found on the outer membrane of Gram-negative bacteria. Bacteria use TAAs in order to infect their host cells via a process called cell adhesion. TAAs also go by another name, oligomeric coiled-coil adhesins, which is shortened to OCAs. In essence, they are virulence factors, factors that make the bacteria harmful and infective to the host organism.

TAAs are just one of many methods bacteria use to infect their hosts, infection resulting in diseases such as pneumonia, sepsis, and meningitis. Most bacteria infect their host through a method named the secretion pathway. TAAs are part of the secretion pathway, to be more specific the type Vc secretion system.

Trimeric autotransporter adhesins have a unique structure. The structure they hold is crucial to their function. They all appear to have a head-stalk-anchor structure. Each TAA is made up of three identical proteins, hence the name trimeric. Once the membrane anchor has been inserted into the outer membrane, the passenger domain passes through it into the host extracellular environment autonomously, hence the description of autotransporter. The head domain, once assembled, then adheres to an element of the host extracellular matrix, for example, collagen, fibronectin, etc.