Evaluating the role of carbonic anhydrases in the transport of HCO3--related species.
Evaluating the role of carbonic anhydrases in the transport of HCO3--related species.
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DOI：
10.1016/j.bbapap.2009.10.021
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发表时间：
2010-02
期刊：
影响因子：
--
通讯作者：
Boron WF
中科院分区：
文献类型：
--
作者：
Boron WF
可溶性酶碳酸酐酶II（CAII）在红细胞（RBC）的CO2流入和流出中起着重要作用，这是一个由细胞外[CO2]变化（CO2启动的CO2运输）引发的过程。有证据表明，CAII可能是红细胞膜内表面大分子复合物的一部分。一些人认为CAII特异性结合Cl-HCO 3交换器AE 1和转运蛋白SLC 4家族的一些其他成员（转运代谢子）的胞质C末端（Ct）上的基序。此外，其他人认为，这种结合CAII增强运输相关的物种-，或离子对-当该过程是通过改变活动的转运（启动运输）。在这篇评论中，我评估的理论作用CA在运输的CO2和相关物种，结论是，虽然结合CAII对CO2引发的CO2运输的影响预计将是巨大的，结合CA对引发运输的影响预计是适度的。我还评估了CAII结合AE 1和其他转运蛋白的实验证据，以及这种结合对启动运输的影响。CAII与AE 1的Ct结合的早期结论似乎是研究中使用的GST融合蛋白中GST不可预测的作用的结果。早期的结论是，结合的CAII加速启动的运输似乎是CAII加速pH变化的结果，用作运输的读出。因此，似乎CAII不直接结合AE 1或其它SLC 4蛋白，并且结合的CAII基本上不加速启动的转运。
The soluble enzyme carbonic anhydrase II (CAII) plays an important role in CO2 influx and efflux by red blood cells (RBCs), a process initiated by changes in the extracellular [CO2] (CO2-initiated CO2 transport). Evidence suggests that CAII may be part of a macromolecular complex at the inner surface of the RBC membrane. Some have suggested CAII specifically binds to a motif on the cytoplasmic C terminus (Ct) of the Cl–HCO3 exchanger AE1 and some other members of the SLC4 family of transporters, a transport metabolon. Moreover, others have suggested that this bound CAII enhances the transport of -related species—, , or ion pairs—when the process is initiated by altering the activity of the transporter (-initiated transport). In this review, I assess the theoretical roles of CAs in the transport of CO2 and -related species, concluding that although the effect of bound CAII on CO2-initiated CO2 transport is expected to be substantial, the effect of bound CAs on -initiated transport is expected to be modest at best. I also assess the experimental evidence for CAII binding to AE1 and other transporters, and the effects of this binding on -initiated transport. The early conclusion that CAII binds to the Ct of AE1 appears to be the result of unpredictable effects of GST in the GST fusion proteins used in the studies. The early conclusion that bound CAII speeds -initiated transport appears to be the result of CAII accelerating the pH changes used as a read-out of transport. Thus, it appears that CAII does not bind directly to AE1 or other SLC4 proteins, and that bound CAII does not substantially accelerate -initiated transport.