The histidine-rich glycoprotein of serum has a domain rich in histidine, proline, and glycine that binds heme and metals.
Histidine-rich glycoprotein (HRG) from rabbit serum was digested with plasmin, reduced, and carboxymethylated, and the fragments produced were resolved by reverse-phase high-performance liquid chromatography. Several peptide fractions were obtained that contain unusually high contents of histidine, proline, and glycine. One His-Pro-Gly-rich peptide (apparent Mr 30 000) was obtained in sufficient yield and purity for further study. This peptide is 29 mol % histidine, 37% proline, and 16% glycine, indicating that most of these three amino acids are located in one region of HRG. The peptide contains 9% by weight carbohydrate and is devoid of tyrosine or tryptophan. The far-ultraviolet circular dichroism spectrum of the peptide has a minimum at 203 nm, indicating that the peptide contains polyproline II helical sections. The peptide represents a binding domain of HRG since it retains much of the ability of intact HRG to bind heme and metals including Zn2+, Ni2+, and Cu2+. As with the parent HRG molecule, interaction of the peptide with heme and metals is dependent on pH and intact histidine residues.
D000818:Animals; D001665:Binding Sites; D002942:Circular Dichroism; D005998:Glycine / Q000032:analysis; D006418:Heme / Q000378:metabolism*; D006639:Histidine / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000378:metabolism*; D008970:Molecular Weight; D011392:Proline / Q000032:analysis; D011506:Proteins / Q000032:analysis* / Q000378:metabolism; D011817:Rabbits; D000099053:Histidine-Rich Glycoprotein
D008670:Metals; D011506:Proteins; D000099053:Histidine-Rich Glycoprotein; D006418:Heme; D006639:Histidine; D011392:Proline; D005998:Glycine