Abstract
Tripeptidylaldehyde (Z-Leu-Leu-Leu-H) is one of the neurite outgrowth factors. Using the affinity chromatography, in which Z-Leu-Leu-Leu-OH is immobilized on the C-terminus, we have arrived at S-100β as a target protein for this drug. In this study, we will report the reactivity of S-100β with Z-Leu-Leu-Leu-H and the analysis on the modification site, relating with a mechanism of neurite outgrowth. S-100β was coupled with Z-Leu-Leu-Leu-H in a neutral buffer containing Ca^<2+>. The modified protein was purified by HPLC, which was eluted at a position different from that of S-100β. MALDI-TOFMS analysis showed that its molecular weight was larger than native S-100β. After treatment with a reducing agent, it was degraded with proteolytic enzymes. Amino acid sequencing of the peptides showed that the ε-amino group of Lys-55 on S-100β was modified with the aldehyde group of Z-Leu-Leu-Leu-H in a possible manner of Schiff base.
