title: Preparation and characterization of an active fragment of colicin E3.
abstract: The conditions of digestion of colicin E3 with trypsin were examined to obtain an active fragment (T2A) of colicin E3, and a method suitable for large-scale preparation of T2A was developed. The T2A preparation thus obtained was homogeneous on SDS-polyacrylamide gel electrophoresis and the molecular weight was estimated to be about 11,000. T2A was composed of 97 amino acid residues and was rich in basic amino acids; methionine, valine, cysteine, and cystine were absent. The N-terminal residue was lysine and the structure near the C-terminus was -Lys-Lys-Tyr-Leu. Since T2A had no lysine or arginine residue at the C-terminus and since the C-terminal structure was identical to that of protein A, it was concluded that T2A was derived from the C-terminal region of protein A. No clear differences were detected among T2A preparations obtained from 3 different fractions of colicin E3, suggesting that the apparent homogeneity of colicin E3 does not involve the T2A region.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002268:Carboxypeptidases; D003087:Colicins; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification*; D012270:Ribosomes / Q000378:metabolism; D014357:Trypsin
chemical_list: D000596:Amino Acids; D003087:Colicins; D010446:Peptide Fragments; D002268:Carboxypeptidases; D014357:Trypsin