RT Journal Article SR Electronic(1) A1 Kusaka, Iwao A1 Matsushita, TakuYR 1987 T1 Characterization of a Ca2+ Uniporter from Bacillus Subtilis by Partial Purification and Reconstitution into Phospholipid Vesicles JF Microbiology, VO 133 IS 5 SP 1337 OP 1342 DO https://doi.org/10.1099/00221287-133-5-1337 PB Microbiology Society, SN 1465-2080, AB Ca2+ was accumulated by right-side-out membrane vesicles of Bacillus subtilis following imposition of a diffusion potential, inside-negative, owing to K+-efflux via valinomycin. Uptake was dependent on the magnitude of the membrane potential. This voltage-dependent Ca2+ uptake was inhibited by Ca2+ channel blockers such as nitrendipine, verapamil and LaCl3, and was competitively inhibited by Ba2+ and Sr2+. The system showed saturation kinetics with an apparent K m for Ca2+ of about 250 μm. Proteins responsible for the voltage-dependent Ca2+ uptake were partially purified by preparative isoelectric focusing in a Sepharose bed. A fraction at pH 5·28–5·33 contained the activity. The characteristics of Ca2+ uptake in reconstituted proteoliposomes were the same as those in membrane vesicles (sensitive to Ca2+ channel blockers; inhibited by Ba2+ and Sr2+). In addition, uptake was not influenced by a pH gradient imposed on the vesicles. The apparent K m for Ca2+ in the reconstituted system was about 260 μm. The specific activity was increased about 50-fold by purification with isoelectric focusing., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-133-5-1337