Interactions of Retinol-Binding Protein with Transthyretin and Its Receptor

To study the interaction of retinol-binding protein (RBP) with its plasma carrier, transthyretin (TTR), spectrofluorimetry, and circular dichroism have previously been used. Both these techniques require milligram quantities of the proteins and this sets limitations on the use of these techniques for the study of RBP-TTR interactions using recombinant proteins. The Escherichia coli expression system described in Chapter 11 does not readily produce milligram quantities of RBP for routine use. For this reason, we have developed a highly sensitive method which employs radioiodmated ¹²⁵ I-RBP (unpublished). The method requires only microgram quantities of protein. This chapter describes a method to radioiodinate RBP without loss of activity and protocols for its use in the study of its interaction with TTR.