title: Neocarzinostatin: effect of modification of side chain amino and carboxyl groups on chemical and biological properties.
abstract: The antitumor protein neocarzinostatin (NCS), isolated from Streptomyces carzinostaticus, is a single chain polypeptide with 109 amino acid residues. Complete acylation of the amino groups (alanine-1 and lysine-20) was observed when NCS was allowed to react with 3-(4-hydroxyphenyl)-propionic acid N-hydroxysuccinimide ester at pH 8.5. Since the ensuing bis[(alanine-1, lysine-20)-3-(4-hydroxyphenyl)]-propionamide NCS was fully active in antibacterial potency and in the inhibition of growth of leukemic (CCRF-CEM) cells in vitro, it appears that the two amino groups in the protein are not essential for biological activity. Radiolabeled NCS was prepared by using a tritiated or 125I-labeled acylating agent. Since the CD spectra of native and bis(alanine-1, lysine-20)-amino modified NCS were indistinguishable, there is presumably no change in the native conformation of the protein due to acylation. Reaction of NCS with ammonium chloride in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at pH 4.75 converted all the 10 carboxyl groups into carboxamides and produced a protein derivative of basic character. This modification caused a change in the native conformation of the protein accompanied by a loss in biological inhibitory activities.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D001681:Biological Assay; D002942:Circular Dichroism; D011199:Potentiometry; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D009353:Zinostatin / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D000903:Antibiotics, Antineoplastic; D009353:Zinostatin