Calcium Binding to Mastocyte Plasma Membrane

Abstract

Rat mastocyte plasma membrane possess two major classes of calcium binding sites which have widely different affinity. At pH 7.5 the low affinity sites can bind about 88 nmol of Ca²⁺ per milligram of membrane protein and are half-saturated at 125 μM Ca²⁺, whereas the high-affinity sites bind about 12 nmol of Ca²⁺ per milligram of membrane protein and are half-saturated at 5.5 μM Ca²⁺. Membrane phospholipids and neuraminic acid residues account for approximately 87% of calcium binding.

Specific Binding Sites for Triiodothyronine in the Plasma Membrane of Rat Thymocytes

“…Progressive (31). With respect to the inhibitory effect of calcium, it is well known that plasma membranes have specific binding sites for calcium (32)(33)(34) and that calcium increases the binding of particular ligands to the plasma membranes of several tissues (35,36), but it is not known whether the binding of calcium initiates the latter responses.…”

Trypsin-induced increase in cyclic AMP concentration in rat thymocytes An effect independent of calcium and calmodulin

“…from three separate experiments: * and ** significantly different from values for trypsin-free thymocytes suspended in standard medium (P < 0.05 and P < 0.01 respectively). 1980;McDonald et al, 1976;Mikkelson & Freerksen, 1980;Porzig & Stoffel, 1978;Reinhart et al, 1984;Tolone et al, 1980;Yamagami & Terayama, 1979). Cyclic AMP concentration Trypsin in various concentrations was incubated with thymocytes for 2 min, and its effect on cellular cyclic AMP concentration was measured.…”