Calcium binding by spinach stromal proteins

Kreimer G, Surek B, Woodrow IE, Latzko E (1987)

Publication Status: Published

Publication Type: Journal article

Publication year: 1987


Publisher: Springer Verlag (Germany)

Book Volume: 171

Pages Range: 259-265

Journal Issue: 2

DOI: 10.1007/BF00391103


Calcium binding to spinach (Spinacia oleracea L.) stromal proteins was examined by dual-wavelength spectrophotometry using the metallochromic indicator tetramethylmurexide. The data are consistent with the existence of at least two, probably independent, classes of binding sites. The total number of binding sites varied between 90–155 nmol·mg−1 protein with “average” binding constants of 1.1–2.7·mM−1. Both Mg2+ and La3+ inhibited calcium binding competitively, with “average” inhibitor constants of 0.26·mM−1 and 39.4·mM−1, respectively; an increase in the potassium concentration up to 50 mM had no effect. In a typical experiment a decrease in pH (7.8 to 7.1) resulted in a decrease in the total number of calcium binding sites from 90 to 59 nmol·mg−1 protein, but in an increase of the “average” affinity from 2.7 to 4.5·mM−1. Calculations, using these data and those of Gross and Hess (1974, Biochim. Biophys. Acta 339, 334–346) for binding site I of washed thylakoid membranes, showed that the free-Ca2+ concentration in the stroma under dark conditions, pH 7.1, is higher than under light conditions, pH 7.8. The physiological relevance of the observed calcium binding by stromal proteins is discussed.

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Kreimer, G., Surek, B., Woodrow, I.E., & Latzko, E. (1987). Calcium binding by spinach stromal proteins. Planta, 171(2), 259-265.


Kreimer, Georg, et al. "Calcium binding by spinach stromal proteins." Planta 171.2 (1987): 259-265.

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