CONICET | Buscador de Institutos y Recursos Humanos

The signal transduction pathway involved in chemotaxis is present with little variations along bacteria and archaea. Chemoreceptor genes, coding for proteins that sense environmental stimuli and transduce the signal to the flagellar motors, are easily recognized in genomic studies due to a highly conserved signaling domain. This domain is implicated in the interaction with the histidin kinase whose activity is modulated in response to stimuli. In E.coli chemoreceptors of same or different specificities are organized in trimers of dimers. Dimer-to-dimer interactions involve a region of the signaling domain. It is not well established, however, whether this organization is a conserved feature that might be central to chemoreceptor function. As a first approach to analize structure and function of non-E.coli chemoreceptors, cloning and expression of a putative aminoacid sensor from P.putida (pctApp) was carried out. The cloned gene was nicely expressed and recognized by antibodies raised against the conserved cytoplasmatic domain from E.coli receptors. Although pctApp expression did not restore chemotaxis to serine in an E.coli strain lacking its native receptor, as assessed in soft agar plates, it did restore the ability to respond to serine in rotational assays. This result indicates that pctApp is able to control the E.coli kinase, presumably through interactions and conformational changes shared with the native transducers. In vivo crosslinking studies indicate that pctApp is not stably incorporated into mixed trimers of dimers with E.coli transducers, but might be able to form trimers of dimers by itself. Presented results and future studies of heterologous chemoreceptors will contribute to elucidate whether the spatial organization of receptors is a conserved feature and a requisite for chemotaxis signaling.