Human monocyte-derived neutrophil chemotactic factor (MDNCF) was purified from culture supernatant of lipopolysaccharide-stimulated human peripheral blood mononuclear leukocytes on a column of Sepharose-bound murine monoclonal anti-MDNCF. About 65% of the culture fluid chemotactic activity was bound to the column. The unbound 35% probably represents chemotactic activity of other cytokines in the culture fluid. More than 85% of the bound activity was eluted by pH 2.5 glycine buffer. When this material was applied to an HPLC-CM column, gradient elution produced four well-separated A280 peaks, each of which had chemotactic activity. N-terminal amino acid analysis of the four peaks revealed three different sequences. One (MDNCF-c) was identical to the sequence that we reported previously. The other two (MDNCF-a and -b) had seven and five additional amino acids, respectively, at the N-terminus. MDNCF-a, -b and -c accounted for 8, 47 and 45% of the total MDNCF peptide. Alignment with the MDNCF cDNA sequence shows that MDNCF-a results from cleavage of a 20 residue signal peptide. MDNCF-c results from culture fluid proteolytic cleavage of the N -terminal sequences of MDNCF-a and -b at an R-S bond. The three peptides occurred in the four HPLC-CM peaks in different ratios. The bulk of any one peptide was distributed in two adjacent HPLC-CM peaks. This suggests that each peptide exists in a minimum of two states. In contrast to our previous multi-step purification, the immunoaffinity and HPLC-CM column sequence resulted in complete purification of MDNCF in two steps and led to identification of two additional MDNCF peptides, one of which has not heretofore been detected.
ASJC Scopus subject areas
- Molecular Biology