Ciaglowski R E, Snow J, Walz D A
Arch Biochem Biophys. 1986 Oct;250(1):249-56. doi: 10.1016/0003-9861(86)90723-x.
Bovine platelet factor 4 was isolated by affinity chromatography using dextran sulfate Sepharose and purified by subsequent gel filtration. The complete amino acid sequence of this 88-residue, 9505-Da protein was determined by isolation and analysis of the overlapping peptides from tryptic and Staphylococcus aureus hydrolysates of reduced, carboxymethylated, and reductive methylated protein. Primary structure comparison was made between bovine platelet factor 4, human platelet factor 4, and human beta-thromboglobulin. The bovine platelet factor 4 amino-terminal region, which contains two unique phenylalanine residues, is extended by 15 residues relative to human platelet factor 4. The bovine carboxy-terminal region is extended by three residues relative to human platelet factor 4 and differed from beta-thromboglobulin in the absence of two additional terminal residues. Bovine platelet factor 4 shares sequence similarities proportionately with both human platelet factor 4 and beta-thromboglobulin. The sequences of the lysine-rich carboxy-terminal putative heparin binding domains are essentially identical for all three proteins. The heparin neutralizing potencies of bovine and human platelet factor 4 are similar: 40 USP units of heparin neutralized per milligram protein, as measured by a modified chromogenic substrate assay. Heparin neutralization was lost by reduction of the disulfide bonds, but only attenuated by tryptic digestion of the intact protein.
通过使用硫酸葡聚糖琼脂糖亲和层析法分离牛血小板因子4，并通过随后的凝胶过滤进行纯化。通过对还原、羧甲基化和还原甲基化蛋白质的胰蛋白酶水解产物和金黄色葡萄球菌水解产物中重叠肽段的分离和分析，确定了这种由88个氨基酸残基组成、分子量为9505道尔顿的蛋白质的完整氨基酸序列。对牛血小板因子4、人血小板因子4和人β-血小板球蛋白进行了一级结构比较。牛血小板因子4的氨基末端区域含有两个独特的苯丙氨酸残基，相对于人血小板因子4延长了15个残基。牛的羧基末端区域相对于人血小板因子4延长了3个残基，并且与β-血小板球蛋白不同之处在于缺少另外两个末端残基。牛血小板因子4与人类血小板因子4和β-血小板球蛋白都按比例共享序列相似性。所有三种蛋白质富含赖氨酸的羧基末端假定肝素结合域的序列基本相同。牛和人血小板因子4的肝素中和能力相似：通过改良的显色底物测定法，每毫克蛋白质可中和40 USP单位的肝素。通过还原二硫键会丧失肝素中和能力，但完整蛋白质经胰蛋白酶消化只会使其减弱。
