Isolation of a low molecular mass vasoactive intestinal peptide binding protein

A vasoactive intestinal peptide (VIP) binding protein was purified in active form by detergent solubilization of lung membranes, gel filtration, VIP-Sepharose affinity chromatography, reverse phase high performance liquid chromatography, and anion exchange chromatography. The mass of this protein was estimated at 18 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 17 kDa by gel filtration. The binding of VIP by this protein was inhibited by Mg2+, covalent cross-linking of [Tyr10-125I]VIP to the protein produced two radioactive bands at 22 and 26 kDa identified by electrophoresis, and the purified protein exhibited saturable and high affinity binding of VIP and the related neuropeptide, rat growth hormone releasing factor.