Characterization of the Ca2+-dependent binding of annexin IV to surfactant protein A.
Characterization of the Ca2+-dependent binding of annexin IV to surfactant protein A.
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DOI：
10.1042/bj3410203
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发表时间：
1999-07
期刊：
影响因子：
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通讯作者：
H. Sohma;C. Creutz;M. Saitoh;H. Sano;Y. Kuroki;D. Voelker;T. Akino
中科院分区：
文献类型：
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作者：
H. Sohma;C. Creutz;M. Saitoh;H. Sano;Y. Kuroki;D. Voelker;T. Akino
我们之前已经证明，表面活性剂蛋白A （SP-A）以Ca2+依赖的方式与膜联蛋白IV结合[Sohma， Matsushima, Watanabe, Hattori， Kuroki和Akino (1995) Biochem]。[j].科学通报，1999,17(2):1 - 8。膜联蛋白IV是膜联蛋白家族的成员，具有大约70个氨基酸的4个一致重复和一个独特的n端尾巴。在本研究中，利用突变蛋白研究了膜联蛋白IV和SP-A对Ca2+依赖性结合的功能位点。SP-A以Ca2+依赖的方式结合到一个由n端结构域和前三个结构域组成的膜联蛋白- iv截断突变体（T(N-1-2-3)）。SP-A也与T3-4结合，但这种相互作用不依赖于Ca2+。SP-A与其他截断突变体（T（N-1-2）、T（2-3）和T(2-3-4)）结合较弱。膜联蛋白IV的每个一致重复序列都具有一个保守的酸性氨基酸残基（Glu70, Asp142， Glu226和Asp301），可以连接Ca2+。使用annexin-IV DE突变体，其中四个Asp/Glu中的一个，两个或三个残基通过位点定向诱变被改变为Ala [Nelson和Creutz (1995) Biochemistry 34,3121 -3132]，发现第三结构域的Ca2+结合比其他Ca2+结合位点更重要。SP-A是与甘露糖结合蛋白a同源的动物凝集素群的成员。大鼠SP-A的Arg197被Asp或Asn取代消除了与膜联蛋白IV的结合，而Glu195被Gln取代则沉默。这些结果表明，Ca2+与膜联蛋白IV结构域3的结合是SP-A Ca2+依赖性结合所必需的，SP-A的Arg197在这种结合中很重要。
We have shown previously that surfactant protein A (SP-A) binds to annexin IV in a Ca2+-dependent manner [Sohma, Matsushima, Watanabe, Hattori, Kuroki and Akino (1995) Biochem. J. 312, 175-181]. Annexin IV is a member of the annexin family having four consensus repeats of about 70 amino acids and a unique N-terminal tail. In the present study, the functional site of both annexin IV and SP-A for the Ca2+-dependent binding was investigated using mutant proteins. SP-A bound in a Ca2+-dependent manner to an annexin-IV truncation mutant consisting of the N-terminal domain and the first three domains (T(N-1-2-3)). SP-A also bound to T3-4, but this interaction was not Ca2+-dependent. SP-A bound weakly to the other truncation mutants (T(N-1-2), T(2-3) and T(2-3-4)). Each consensus repeat of annexin IV possesses a conserved acidic amino acid residue (Glu70, Asp142, Glu226 and Asp301) that putatively ligates Ca2+. Using annexin-IV DE mutants in which one, two or three residues out of the four Asp/Glu were altered to Ala by site-directed mutagenesis [Nelson and Creutz (1995) Biochemistry 34, 3121-3132], it was revealed that Ca2+ binding in the third domain is more important than in the other Ca2+-binding sites. SP-A is a member of the animal lectin group homologous with mannose-binding protein A. The substitution of Arg197 of rat SP-A with Asp or Asn eliminated binding to annexin IV, whereas the substitution of Glu195 with Gln was silent. These results suggest that the Ca2+ binding to domain 3 of annexin IV is required for the Ca2+-dependent binding by SP-A and that Arg197 of SP-A is important in this binding.