C4b-binding protein protects coagulation factor Va from inactivation by activated protein C.
C4b-binding protein protects coagulation factor Va from inactivation by activated protein C.
复制标题
C4b 结合蛋白可保护凝血因子 Va 免遭活化蛋白 C 失活。
DOI：
10.1021/bi0006058
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发表时间：
2000
期刊：
影响因子：
2.9
通讯作者：
Bonno N. Bouma
中科院分区：
文献类型：
--
作者：
R. V. D. Poel;Joost C. M. Meijers;J. Rosing;G. Tans;Bonno N. Bouma
我们研究了在蛋白S存在和不存在的情况下，C4 BP对APC介导的因子Va（FVa）失活的影响。FVa失活是双相的（k（506）= 4.4 × 10（8）M（-）（1）s（-）（1），k（306）= 2.7 × 10（7）M（-）（1）s（-）（1）），并且蛋白S加速Arg（306）裂解约10倍。蛋白S与C4 BP的预孵育导致蛋白S辅因子活性的完全废除。C4 BP还在蛋白S不存在的情况下保护FVa免于APC的失活。用CLB-PS13（一种单克隆抗蛋白S抗体）进行的对照实验表明，C4 BP对FVa失活的抑制不是通过我们的反应系统中污染痕量的蛋白S介导的。FVa的保护被针对C4 BP α链的单克隆抗体阻止。仅由α链组成的重组rC 4 BPalpha也保护FVa，但在蛋白S存在下，保护水平降低，因为rC 4 BPalpha缺乏负责C4 BP与蛋白S结合的β链。截短的C4 BP β链（SCR-1+2）抑制蛋白S辅因子活性，但在不存在蛋白S的情况下对APC引起的FVa失活没有影响。总之，C4 BP通过C4 BP的α-链与FVa和/或APC的直接相互作用以蛋白S非依赖性方式保护FVa免于APC催化的切割。
We investigated the effect of C4BP on APC-mediated inactivation of factor Va (FVa) in the absence and presence of protein S. FVa inactivation was biphasic (k(506) = 4.4 x 10(8) M(-)(1) s(-)(1), k(306) = 2.7 x 10(7) M(-)(1) s(-)(1)), and protein S accelerated Arg(306) cleavage approximately 10-fold. Preincubation of protein S with C4BP resulted in a total abrogation of protein S cofactor activity. C4BP also protected FVa from inactivation by APC in the absence of protein S. Control experiments with CLB-PS13, a monoclonal anti-protein S antibody, indicated that inhibition of FVa inactivation by C4BP was not mediated through contaminating traces of protein S in our reaction systems. Protection of FVa was prevented by a monoclonal antibody directed against the C4BP alpha-chain. Recombinant rC4BPalpha comprised of only alpha-chains also protected FVa, but in the presence of protein S, the level of protection was decreased, since rC4BPalpha lacks the beta-chain responsible for C4BP binding to protein S. A truncated C4BP beta-chain (SCR-1+2) inhibited protein S cofactor activity, but had no effect on FVa inactivation by APC in the absence of protein S. In conclusion, C4BP protects FVa from APC-catalyzed cleavage in a protein S-independent way through direct interactions of the alpha-chaims of C4BP with FVa and/or APC.