Complex formation between a formyl peptide and 24p3 protein with a blocked N‐terminus of pyroglutamate

Abstract

We have purified 24p3 protein from mouse uterine fluid (Biochem. J.316, 545–550, 1996). It is a 25.8‐kDa glycoprotein with a N‐blocked terminus. This work demonstrated the N‐blocked residue to be pyroglutamate, supporting the post‐translational cleavage site at Ala‐Gln in the precursor protein to generate a putative protein of 180 amino acid residues. Consequently, the two cysteines, Cys⁷⁸ and Cys¹⁷⁷, and the two tryptophans, Trp³¹ and Trp⁸¹, are assigned along the polypeptide chain. No free thiol group was detected in the protein. The presence of formyl‐Met‐Leu‐Phe in the protein solution causes a considerable decrease in the protein fluorescence due to Trp³¹ and Trp⁸¹. Analysis of the fluorescence data supports the idea that the protein can be complexed with the formyl peptide. The association constant for the complex formation is (4.8 ± 0.29) × 10⁵ M^‐1 at pH 7.4.