DeLa Cadena R A, Kunapuli S P, Walz D A, Colman R W
Sol Sherry Thrombosis Research Center, and Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Thromb Haemost. 1998 Jan;79(1):186-94.
Platelet thrombospondin (TSP1) forms a complex with high (HK) and low (LK) molecular weight kininogens. We isolated a proteolytic fragment from HK and LK heavy chains (12 kDa) recognized by TSP1 with a N-terminal sequence, K244ICVGCPRDIP254. Lys244-Pro254 oxidized to cyclic form prevented binding of 125I-LK to TSP1. This effect was abolished by reduction and alkylation. Oxidized peptide KICVGCPRDIP (100 microM) reversed the known inhibitory effects of LK or HK (1 microM), on thrombin-induced platelet activation, suggesting this peptide forms part of the cell binding site on HK and LK for activated platelets. KICVGCPRDIP completely inhibited the binding of 125I-LK to activated platelets. However, the peptide only partially inhibited binding of 125I-HK to platelets, suggesting an additional binding site on the HK light chain. Fluorescein-labeled KICVGCPRDIP bound directly and specifically to activated platelets. A monoclonal antibody directed to TSP1 partially inhibited the binding of 125I-HK to activated but not inactivated platelets. We conclude residues Lys244-Pro254 on kininogen heavy chain is responsible for binding to thrombospondin on the surface of activated platelets.
血小板凝血酶敏感蛋白（TSP1）与高分子量（HK）和低分子量（LK）激肽原形成复合物。我们从HK和LK重链中分离出一个被TSP1识别的蛋白水解片段（12 kDa），其N端序列为K244ICVGCPRDIP254。Lys244 - Pro254氧化成环状形式可阻止125I - LK与TSP1结合。还原和烷基化可消除这种作用。氧化肽KICVGCPRDIP（100 microM）可逆转LK或HK（1 microM）对凝血酶诱导的血小板活化的已知抑制作用，表明该肽是HK和LK上活化血小板细胞结合位点的一部分。KICVGCPRDIP完全抑制125I - LK与活化血小板的结合。然而，该肽仅部分抑制125I - HK与血小板的结合，提示HK轻链上存在额外的结合位点。荧光素标记的KICVGCPRDIP直接且特异性地结合活化血小板。一种针对TSP1的单克隆抗体部分抑制125I - HK与活化但未失活血小板的结合。我们得出结论，激肽原重链上的Lys244 - Pro254残基负责与活化血小板表面的凝血酶敏感蛋白结合。
