Pierce into the Native Structure of Ata, a Trimeric Autotransporter of Acinetobacter baumannii ATCC 17978

Abstract

Acinetobacter baumannii is an important pathogen responsible for nosocomial infections worldwide. Trimeric autotransporters, the obligate homotrimeric adhesins, are involved in adherence of bacterial cells to various surfaces. These sorts of adhesins were shown to be expressed by A. baumannii. Trimeric autotransporters are modular virulence factors, containing numerous domains and structural architectures. The better understanding of the sequence and structural features of virulence factors are crucial in designing new therapeutic strategies. In this regard, with the aid of reliable in silico tools and the concept of “inherence through homology”, some sequence and structural features of AtaA.baumannii were unveiled. Domain architectures such as the position of repetitive modules, and coiled-coils, along with the prediction of tertiary and quaternary structures, allows us to define some important landscapes of AtaA.baumannii virulence factor. In addition, through CLANS analysis of TAA sequences of Moraxellaceae family, it was concluded that Ata contains several conserved of structural blocks of TAAs. The protein is initiated with extended signal peptide region, a stalk of several head domains and a membrane anchoring region. The globular heads are connected to each other by neck mediators and coiled-coil regions. Several fibronectin and collagen binding sites were defined within the structures. Minimal and maximal frustrated contacts are distributed within the structure of Ata, which suggest both the flexibility and toughness. These are come together for creating an efficient adhesin which is able to bind and bend through multiple sites. The protein could be great target for designing new vaccines or anti-virulence drug.