Hypothesis for a serine proteinase-like domain at the COOH terminus of Slowpoke calcium-activated potassium channels.
Hypothesis for a serine proteinase-like domain at the COOH terminus of Slowpoke calcium-activated potassium channels.
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DOI：
10.1085/jgp.108.6.473
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发表时间：
1996-12
影响因子：
3.8
通讯作者：
Moczydlowski, E
中科院分区：
文献类型：
--
作者：
Moss, GWJ;Marshall, J;Moczydlowski, E
关键词：
牛胰蛋白酶抑制因子(BPTI)是一种由58个残基组成的含三个二硫键的蛋白质，属于昆尼茨丝氨酸蛋白酶抑制剂家族。BPTI是一种非常有效的胰酶抑制剂，但它也能与Kd值超过8个数量级的各种活性和非活性丝氨酸蛋白酶同系物特异性结合。我们以前描述了BPTI在细胞内位置的相互作用，导致在大电导钙激活的K+通道(MOSS，G.W.J.和E.Moczydlowski)中产生离散的亚电导事件。1996，J.Gen.Physiol，107：47-68)。在本文中，我们总结了各种积累的证据，表明BPTI与KCA通道蛋白上的一个位置结合，该位置在结构上类似于丝氨酸蛋白酶。一条证据包括发现BPTI和胰酶的复合体，其中BPTI的抑制环被与胰酶的相互作用掩盖，在KCA通道中产生亚状态事件完全无效。为了进一步研究这一概念，我们对从果蝇和哺乳动物克隆的慢拨KCA通道的阿尔法亚单位进行了序列分析。这一分析表明，KCA通道COOH末端附近约250个残基与丝氨酸蛋白酶家族成员同源，但由于关键催化残基的各种替换而在催化上无效。序列分析还预测了在许多丝氨酸蛋白酶中发现的钙结合环的位置。我们推测，慢卒中KCA通道的这个COOH-末端结构域采用丝氨酸蛋白酶特有的双筒折叠，参与通道的Ca(2+)激活，也可能与调节KCA通道活性的其他细胞内成分结合。
Bovine pancreatic trypsin inhibitor (BPTI) is a 58-residue protein with three disulfide bonds that belongs to the Kunitz family of serine proteinase inhibitors. BPTI is an extremely potent inhibitor of trypsin, but it also specifically binds to various active and inactive serine proteinase homologs with KD values that range over eight orders of magnitude. We previously described an interaction of BPTI at an intracellular site that results in the production of discrete subconductance events in large conductance Ca2+ activated K+ channels (Moss, G.W.J., and E. Moczydlowski. 1996, J. Gen. Physiol, 107:47-68). In this paper, we summarize a variety of accumulated evidence which suggests that BPTI binds to a site on the KCa channel protein that structurally resembles a serine proteinase. One line of evidence includes the finding that the complex of BPTI and trypsin, in which the inhibitory loop of BPTI is masked by interaction with trypsin, is completely ineffective in the production of substate events in the KCa channel. To further investigate this notion, we performed a sequence analysis of the alpha-subunit of cloned slowpoke KCa channels from Drosophila and mammals. This analysis suggests that a region of approximately 250 residues near the COOH terminus of the KCa channel is homologous to members of the serine proteinase family, but is catalytically inactive because of various substitutions of key catalytic residues. The sequence analysis also predicts the location of a Ca(2+)-binding loop that is found in many serine proteinase enzymes. We hypothesize that this COOH-terminal domain of the slowpoke KCa channel adopts the characteristic double-barrel fold of serine proteinases, is involved in Ca(2+)-activation of the channel, and may also bind other intracellular components that regulate KCa channel activity.
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影响因子：
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通讯作者：
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