Figure 5.

Kinetic scheme for interaction between receptors and a common pool of Lyn kinase. In this figure, Lyn placed to the left of the receptor R_i refers to the constitutively associated kinase; Lyn placed to the right of phosphorylated R_i − P refers to recruited kinase (15, 16). In the latter species, no constitutively associated kinase is shown simply to avoid complicating the figure. Whether such species continue to interact with Lyn at their presumed site of constitutive interaction is not known. Our schematic representation is also not meant to rule out the possibility that Lyn bound to the phosphorylated receptors may be different than the Lyn bound constitutively. X refers to any non-FcɛRI that may be able to interact with Lyn constitutively or after phosphorylation or both. n to the left of R_i refers to monomeric receptors where n ≥ 1; n as a superscript refers to an aggregate of R_i where n ≥ 2. P refers to phosphotyrosine. The slanted arrows refer to the disposition of Lyn; the vertical and horizontal arrows to the disposition of the entire complex. The horizontal arrows on the left are shown as dashed because the direction of the equilibrium will depend upon the binding constant of the aggregating stimulus for the IgE (if the stimulus is antigen) or for the receptor (if the stimulus is oligomer).