| Comments |
P.419 right column 3rd paragraph: "Ca2+ provision directly through cytosol: Concerning the second transport hypothesis, it will be calculated, if enough Ca2+ can be made available via a transmembrane transport from the cytosol. The import of Ca2+ directly across the CV [coccolith vesicle] membrane is calculated by means of known kinetic values for Ca2+-ATPases (Table 3). Ca2+-ATPases are ATP-driven Ca2+/H+ exchangers of the sarcoplasmic reticulum (SR) membrane found in mammalian muscle cells that pump Ca2+ from the cytosol to the SR lumen with a molar stoichiometry of 2 Ca2+ : 1 ATP : 2–3 H+ (Møller et al. 2010). Expressed sequence tag clusters similar to those of Ca2+-ATPases have been located in E. huxleyi by von Dassow et al. (2009). According to the values given in Table 3, up to 21 fmol Ca2+ can be provided for coccolith synthesis which comes close to the required 22 fmol Ca2+ (one complete coccolith)." See note above table |