Interaction of spin-labeled silver hake parvalbumin with metal ions and model membranes

The precise physiological function of parvalbumins is not yet known. As part of the search for functional relevance, it is logical to examine the interaction between parvalbumins and various cellular components, including interactions with other intracellular proteins, biological metal ions (such as Ca2+ and Mg2+), and membranes. In this paper, interactions of the major silver hake parvalbumin isotype with metal ions and with two types of model biological membranes (i.e., 1,2-Di-O-Hexadecyl-rac-glycero-3-PhosphoCholine, DHPC, vesicles and sodium dodecyl sulfate, SDS, micelles) are revealed by means of spin-label electron paramagnetic resonance (EPR) spectroscopy. (Up until a few years ago it was generally assumed that parvalbumins do not interact with cell membranes.) Our EPR results will clearly show that spin-labeled tyrosine silver hake parvalbumin-B interacts with both vesicles and micelles in the absence and in the presence of Ca2+ ions, although the interaction is significantly greater in the absence of Ca2+. Our results support the findings of Permyakov et al. (E. A. Permyakov, D. I. Kreimer, L. P. Kalinichenko, A. A. Orlova, and V. L. Shnyrov, Cell Calcium 10, 71 (1989)), based on gel-chromatography, electron microscopy, intrinsic protein fluorescence, and microcalorimetry methods, that parvalbumin (especially in the absence of Ca2+) interacts with model biological membranes.