GENERATION OF CHIMERIC C5A FORMYL PEPTIDE RECEPTORS - TOWARDS THE IDENTIFICATION OF THE HUMAN C5A RECEPTOR-BINDING SITE/

We employed the polymerase chain reaction to produce a series of chime ric C5a/formyl peptide receptors. Chinese hamster ovary cells transfec ted with these constructs were tested for their ability to bind C5a. S ubstitution of three of the extracellular domains of the C5a receptor with the corresponding domains of the formyl peptide receptor abolishe d C5a binding, whilst replacement of the first extracellular loop of t he C5a receptor with that of the formyl peptide receptor had little ef fect on the affinity of the receptor for C5a. We therefore conclude th at this first outer loop of the C5a receptor does not participate in l igand binding, whilst involvement of the other extracellular domains o f the receptor cannot be ruled out.