Determination of the cross-linked residues in homo-dimerization of S19 ribosomal protein concomitant with exhibition of monocyte chemotactic activity.

When S19 ribosomal protein molecules are intermolecularly cross-linked by a transglutaminase-catalyzed reaction, the monocyte chemotactic activity is newly expressed. Heparin, at a concentration of 1 U/ml, greatly augmented the cross-linking reaction. This augmentation was due to binding affinity of S19 ribosomal protein to heparin. The major heparin-binding region of S19 ribosomal proteins was identified to Lys23-Lys-Ser-Gly-Lys-Leu-Lys29, using region-directed mutant proteins. The amino acid residues of S19 ribosomal protein used for the intermolecular cross-linkage were then determined by the peptide map analysis with amino acid sequencing and by the site-directed mutagenesis; Gln137 and Lys122 were used in the intermolecular cross-linkage.