Na+/H+ antiporters are ubiquitous membrane proteins and play an important role in cell homeostasis. We amplified a gene encoding a member of the monovalent cation:proton antiporter‐2 (CPA2) family (TC 2.A.37) from the Thermus thermophilus genome and expressed it in Escherichia coli. The gene product was identified as a member of the NapA subfamily and was found to be an active Na+(Li+)/H+ antiporter as it conferred resistance to the Na+ and Li+ sensitive strain E. coli EP432 (ΔnhaA, ΔnhaB) upon exposure to high concentration of these salts in the growth medium. Fluorescence measurements using the pH sensitive dye 9‐amino‐6‐chloro‐2‐methoxyacridine in everted membrane vesicles of complemented E. coli EP432 showed high Li+/H+ exchange activity at pH 6, but marginal Na+/H+ antiport activity. Towards more alkaline conditions, Na+/H+ exchange activity increased to a relative maximum at pH 8, where by contrast the Li+/H+ exchange activity reached its relative minimum. Substitution of conserved residues D156 and D157 (located in the putative transmembrane helix 6) with Ala resulted in the complete loss of Na+/H+ activity. Mutation of K305 (putative transmembrane helix 10) to Ala resulted in a compromised phenotype characterized by an increase in apparent K m for Na+ (36 vs. 7.6 mM for the wildtype) and Li+ (17 vs. 0.22 mM), In summary, the Na+/H+ antiport activity profile of the NapA type transporter of T. thermophilus resembles that of NhaA from E. coli, whereas in contrast to NhaA the T. thermophilus NapA antiporter is characterized by high Li+/H+ antiport activity at acidic pH.

BackgroundSurvival and success rates of tooth transplantations even after long follow-up periods have been shown to be very high. Nevertheless, it is important to analyse factors potentially influencing these rates. The aim of this study was to assess the influence on success of potential factors.MethodsThe research was based on a retrospective analysis of clinical and radiological data from a sample of 59 subjects (75 transplanted teeth). The follow-up period varied from 0.44 to 12.28 years (mean 3.95 years). Success rates were calculated and depicted with Kaplan-Meier plots. Log-rank tests were used to analyse the effect of root development stage, apex width, the use of enamel matrix proteins or the surgeon on success of transplantations.ResultsResults for success of premolar transplantations were comparable with already published data, while molars performed worse than shown in other studies. The surgeon performing the transplantation (p = 0.001) and tooth type (p ≤ 0.001) were significantly associated with transplantation success. Use of enamel matrix proteins (p = 0.10), root development stage (p = 0.13), the recipient area (p = 0.48) and apex width (p = 0.59) were not significantly associated with success.ConclusionsMolar transplantations were not as successful as premolar transplantations; however, success rates varied greatly depending on the surgeon’s experience. The use of enamel matrix proteins as well as root development stage, the recipient area and apex width did not show significant associations with success of tooth transplantations.