Kup and KimA: Two secondary transporters involved in the homeostasis of K+ in Enterococcus faecalis.

ESPARIZ, MARTÍN; BLANCATO, VÍCTOR; ACCIARRI, GIULIANA; MAGNI, CHRISTIAN

Congreso; LIV REUNION ANUAL SOCIEDAD ARGENTINA DE INVESTIGACION EN BIOQUIMICA Y BIOLOGIA MOLECULAR; 2020

E. faecalis are facultative anaerobic Gram-positive bacteria and constitute part of the normal intestinal flora of humans. In recent years however,it has emerged as a clinical important opportunistic pathogen. The robust physiology of these bacteria facilitates tolerance to various stresses.Despite its controversial profile, E. faecalis are part of food products, either due to contamination or as part of starter, adjunct or non-startercultures. Besides, ion homeostasis is a key factor for all living cells. Particularly, potassium (K+) is the most abundant cation in the cytosol, andits uptake is tightly regulated. Intracellular K+ is important for cellular metabolic processes such as gene expression, pH homeostasis, osmoticadaptation and enzymatic activity. A search for genes present in E. faecalis genome coding for proteins with high homology for K+ transportersand a subsequent topology analysis, revealed the presence of a Kup as well as a KimA homologue. These proteins are regulated by the secondarymessenger c-di-AMP in L. lactis and B. subtilis, respectively. To study the functional properties of the proteins encoded by both genes we usedE.coli LB650 (ΔkdpABC5 ΔtrkH ΔtrkG). This strain is a triple mutant for the main K+ transporter systems and, hence, it is unable to grow at lowK+ concentrations. E. faecalis JH2-2 kup and kimA genes were individually cloned in plasmid pWH844 using E. coli LB650 as host, to check iftheir expression could restore growth in minimal salt media when no KCl is added. Both evidence growth with or without K+ supplementation.These results suggest that Kup and KimA are involved in the K+ transport in. E. faecalis.