SOLUBILIZATION OF BINDING-SITES FOR IAPP AND CGRP FROM RAT LUNG

Functional binding sites for [I-125]APP and [I-125]CGRP were solubilized from rat lung membranes with CHAPSO (10 nM). Rat IAPP had a higher affinity (K-i = 22.9 nM) for [I-125]IAPP binding and rat alpha CGRP (K-i = 0.904 nM) had a higher affinity for [I-125]CGRP binding over related peptides. [I-125]IAPP binding was unaffected by GTP gamma S, but [I-125]CGRP binding was 50% inhibited, indicating solubilization of a G-protein-receptor complex for CGRP but not IAPP binding. Wheat germ agglutinin affinity columns gave a 25-fold purification of IAPP binding sites, but no CGRP binding sites were eluted from the column, indicating different patterns of glycosylation of the two sites.