Amino acid sequence of human platelet factor 4

Area of Science:

• Biochemistry
• Protein Chemistry
• Molecular Biology

Background:

• Human platelet factor 4 (PF4) is a protein known to bind heparin.
• Understanding the structure of PF4 is crucial for elucidating its biological functions, particularly its interaction with heparin.

Purpose of the Study:

• To purify human platelet factor 4 (PF4) to homogeneity.
• To determine the complete amino acid sequence of PF4.
• To investigate the structural basis for heparin binding.

Main Methods:

• Protein purification techniques to achieve homogeneity.
• Amino acid sequencing to determine the polypeptide chain composition.
• Analysis of amino acid distribution and sequence patterns.

Main Results:

• PF4 was purified to apparent homogeneity.
• The complete amino acid sequence of the 70-residue polypeptide was determined.
• The sequence revealed a lack of methionine, tryptophan, and phenylalanine, with only one tyrosyl residue.
• A highly negatively charged amino-terminal region was identified.
• An unusual carboxyl-terminal region with repetitive clusters of charged and hydrophobic amino acid pairs was found.

Conclusions:

• The complete amino acid sequence of human PF4 was established.
• The unique structural features of the carboxyl-terminal region suggest a potential role in heparin binding.