J. Biol. Chem., Vol. 268, Issue 4, 2292-2295, Feb, 1993
Formyl peptide receptor chimeras define domains involved in ligand binding
HD Perez, R Holmes, LR Vilander, RR Adams, W Manzana, D Jolley and WH Andrews
Department of Medicine, University of California, San Francisco 94143.
We have begun to study the structural requirements for the binding of
formyl peptides to their specific receptors. As an initial approach, we
constructed C5a-formyl peptide receptor chimeras. Unique (and identical)
restriction sites were introduced within the transmembrane domains of these
receptors that allowed for the exchange of specific areas. Four types of
chimeric receptors were generated. 1) The C5a receptor was progressively
substituted by the formyl peptide receptor. 2) The formyl peptide receptor
was progressively substituted by the C5a receptor. 3) Specific domains of
the C5a receptor were substituted by the corresponding domain of the formyl
peptide receptor. 4) Specific domains of the formyl peptide receptor were
replaced by the same corresponding domain of the C5a receptor. Wild type
and chimeric receptors were transfected into COS 7 cells and their ability
to bind formyl peptide determined, taking into account efficiency of
transfection and expression of chimeric protein. Based on these results, a
ligand binding model is presented in which the second, third, and fourth
extracellular (and/or their transmembrane) domains together with the first
transmembrane domain form a ligand binding pocket for formyl peptides. It
is proposed that the amino-terminal domain plays a role by presumably
providing a "lid" to the pocket. The carboxyl-terminal cytoplasmic tail
appears to modulate ligand binding by regulating receptor affinity.
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