J. Biol. Chem., Vol. 255, Issue 7, 2886-2896, Apr, 1980
Primary structure of a histidine-rich proteolytic fragment of human ceruloplasmin. II. Amino acid sequence of the tryptic peptides
IB Kingston, BL Kingston and FW Putnam
Amino acid sequence studies of tryptic peptides isolated from a
histidine-rich fragment (Cp F5) of human ceruloplasmin are described.
Nineteen tryptic peptides were isolated from unmodified Cp F5 and five
tryptic peptides were isolated from citraconylated Cp F5. These peptides,
together with the cyanogen bromide fragments reported previously, allowed
the assembly of the complete sequence of Cp F5. The fragment has 159
residues and a molecular weight of 18,650; it lacks carbohydrate, is rich
in histidine, and contains 1 free cysteine that may be part of a
copper-binding site. Human ceruloplasmin is a single polypeptide chain with
a molecular weight of about 130,000 that is readily cleaved to large
fragments by proteolytic enzymes; the relationships of Cp F5 to intact
ceruloplasmin and to structural subunits earlier proposed is described. Cp
F5 probably is an intact globular domain that is attached to the
COOH-terminal end of ceruloplasmin by a labile interdomain peptide bond.