A calcium binding protein from cell wall of Neurospora crassa

Isolated cell wall preparations of N. crassa bind significant levels of Ca, Mg and other divalent cations. Enzymatic treatment of the cell wall with β‐(1,3)‐glucanase, but not with chitinase, resulted in solubilization of only the calcium‐binding protein fraction. A calcium‐binding protein (CaBP) was purified by metal‐chelate affinity chromatography and reversed phase HPLC. CaBP has an Mr of around 6 kDa on SDS‐PAGE and mass spectrometry showed that it has a molecular mass of 5744 Da. One mole of CaBP binds 2 moles of calcium and is partially inhibited (15–50%) by other divalent cations (Mg, Ni and Cu). Quenching of tryptophan fluorescence was observed upon copper binding but not calcium binding. This is a first report of a calcium binding protein from the cell wall of fungi. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)