ROLE OF DIFFERENT COUPLING CHEW PROTEINS IN THE CHEMOTAXIS-RELATED PATHWAYS OF THE HYDROCARBONDEGRADING STRAIN Halomonas titanicae KHS3

RAMOS RICCIUTI, F.E.; BALMACEDA, R.S.; HERRERA SEITZ, M.K.; STUDDERT, C. A.

Buenos Aires

Congreso; Reunión Conjunta de Sociedades Científicas 2017; 2017

SAIB

In the canonical E. coli chemotaxis pathway, chemoreceptors transmit information from the extracellular medium to an associated histidine kinase (CheA), through a coupling protein (CheW). Many environmental bacteria possess more than one chemosensory pathway. The protein components show a high conservation and mechanisms that avoid crosstalk between the different pathways are not clear yet.Halomonas titanicae KHS3 was isolated from Mar del Plata harbor. It can grow using polyaromatic hydrocarbons as the sole carbon source and displays chemotactic behavior toward these compounds.Two chemotaxis-related systems were identified in its genomic sequence. Cluster 1 has a canonical organization, similar to the E. coli che cluster. On the other hand, cluster 2 shows a different gene organization including a diguanylate cyclase protein and two CheW-like coupling proteins.The aim of this work was to investigate the properties of the different CheW proteins. The three proteins were modelled using Swissmodel software. Both Ht CheW1 and CheW2 showed a structure similar to E. coli CheW whereas Ht CheW3 displayed an structure that deviated from the conserved one, suggesting a different role. . CheW1 and CheW2 were expressed in E. coli cells. CheW1, from cluster 1, complemented chemotaxis function in an E. coli strain lacking native CheW in soft agar plates, indicating that it fulfills a similar role in complexes that control flagellar rotation. When expressed at very high levels, it interfered with chemotactic function, consistent with the ability of CheW proteins to interact with chemoreceptor dimers and disrupt important receptor-receptor interactions.In contrast, CheW2 failed to restore chemotactic function, and did not interfere with E. coli chemotaxis, even when overexpressed. This indicates that CheW2 does not interact with E. coli chemoreceptors, suggesting that it has specificity determinants for proper interactions with cognate receptors.