ISSN:
1432-2048
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Using recently developed techniques, we have investigated the binding of 45Ca2+ to membrane preparations from corn (Zea mays L) and oat (Avena sativa L) coleoptile tissue. Scatchard plot analysis reveals at least two Ca2+-binding sites in each tissue, a high affinity binding site (K m=7.7×10-7 M, n=6.9×10-10 mol·0.5 g f.w.-1 in corn, K m=4.93×10-6 M, n=2.29×10-9 mol·0.5 g f.w.-1 in Avena) and a low affinity binding site (K m=9.01×10-5 M, n=5.4×10-8 mol·0.5 g f.w.-1 in corn; K m=1.03×10-4 M, n=3.40×10-8 mol·0.5 g f.w.-1 in Avena). There is also some evidence of a third, lower affinity binding site in each tissue, especially corn. More detailed studies with corn coleoptile homogenates show that they contain a potent dialyzable inhibitor of Ca2+ binding. Monovalent cations were observed to be ineffective as inhibitors of Ca2+ binding in corn. However, of six divalent cations tested, all were capable of strong inhibition of Ca2+-binding and there appeared to be a relationship between size of the atomic radius of the ion and potency as an inhibitor of calcium binding.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00387836
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