Horse spleen apoferritin: N-terminal and C-terminal residues

Abstract

The presence of an N-acetyl serine residue at the N-terminal side of the peptide chain of the apoferritin subunits has been confirmed. Quantitative determination of the bound acetyl groups gives a value of 19.6 ± 1 moles per mole apoferritin (mol. wt. 480,000). No amino acids are liberated by carboxypeptidase A. Carboxypeptidase B releases 18–19 moles of arginine and over 15 moles of lysine per mole of apoferritin. The C-terminal peptide has been isolated. It has the sequence Ser-Gln-Gly-Asn-Ala-Leu-Lys-Arg. These results are consistent with earlier findings that apoferritin consists of 20 identical subunits.