Echovirus-9 protein 2C binds single-stranded RNA unspecifically.

Polypeptide 2C is essential for picornavirus replication. Although many data on multiple functions of this highly conserved protein are available, the mechanism of RNA binding is still obscure. In this work, protein 2C of echovirus-9 strain Barty was expressed as a histidine-tagged protein in E. coli followed by nondenaturing purification to homogeneity. After incubation of 2C protein with different kinds of RNA fragments, binding was shown in gel retardation assays. Competition experiments revealed that 2C targets linear RNA unspecifically; however, single-stranded linear DNA does not react with this protein. In contrast to poliovirus, protein 2C of echovirus-9 only recognizes RNA with a low content of secondary structures. This may be a first hint of a different binding specificity of 2C in echo- and polioviruses.

Integrin alpha(v)beta3 (vitronectin receptor) is a candidate receptor for the virulent echovirus 9 strain Barty.

The enterovirus echovirus 9 strain Barty (E9/Barty) is pathogenic for newborn mice as well as for humans. In contrast to the apathogenic prototype strain Hill, strain Barty encodes an RGD motif in the C-terminal part of the structural protein VP1. Data are presented that show that E9/Barty binds its target cells via contact of the RGD motif to the alpha(v)beta3 integrin (vitronectin receptor), whereas prototype Hill uses a different, still unidentified receptor site. Furthermore, virus titres of murine muscle tissue were compared after infection of newborn and 1-, 2-, 3- and 12-week-old mice. The replication capacity of the virus decreased dramatically with age of the infected mice. Since E9/Barty does not replicate or replicates only poorly in mice older than about 5 days, and expression of the vitronectin receptor is reported to be down-regulated in striated muscle tissue during development, it is suggested that susceptibility of mice to this echovirus infection is controlled by the availability of alpha(v)beta3 integrin.