Deuel T F, Keim P S, Farmer M, Heinrikson R L
Proc Natl Acad Sci U S A. 1977 Jun;74(6):2256-8. doi: 10.1073/pnas.74.6.2256.
Human platelet factor 4, a protein that binds heparin, has been purified to apparent homogeneity and the complete amino acid sequence of the protein has been determined. The 70-residue polypeptide chain contains no methionine, tryptophan, or phenylalanine, and contains only a single tyrosyl residue. The sequence analysis demonstrates a highly negatively charged amino-terminal region. The carboxyl-terminal region of the polypeptide is unusual in that it contains a repetitive clustering of positively charged and hydrophobic pairs of amino acids; preliminary evidence suggests that this domain may play a role in the binding of heparin.