Pope B, Way M, Weeds A G
MRC Laboratory of Molecular Biology, Cambridge, UK.
FEBS Lett. 1991 Mar 11;280(1):70-4. doi: 10.1016/0014-5793(91)80206-i.
Gelsolin binds two monomers in the nucleating complex with G-actin in calcium and caps actin filaments. However, 3 actin-binding domains have been identified within its 6 repeating sequence segments corresponding to S1 S2-3 and S4-6. S1 and S4-6 bind only G-actin whereas S2-3 binds specifically to F-actin. Two of the three domains (S2-3 and S4-6) are required for nucleation and a different pair (S1 and S2-3) for severing. Here we show for the first time that the domains unique to nucleation (S4-6) or severing (S1) compete for the same region on subdomain 1 of G-actin. We further show that S2-3 binds actin monomers weakly in G-buffer conditions and that this interaction persists when S1 or S4-6 are also bound. Thus gelsolin associates with two distinct regions on actin. Since S2-3 does not bind monomeric actin in F-buffer, we suggest that its high affinity 1:1 stoichiometry for filament subunits reflects interaction with two adjacent subunits.
凝溶胶蛋白在有钙存在的情况下，与成核复合物中的两个肌动蛋白单体以及G - 肌动蛋白结合，并封闭肌动蛋白丝。然而，在其对应于S1、S2 - 3和S4 - 6的6个重复序列片段中已鉴定出3个肌动蛋白结合结构域。S1和S4 - 6仅结合G - 肌动蛋白，而S2 - 3特异性结合F - 肌动蛋白。成核需要三个结构域中的两个（S2 - 3和S4 - 6），切断则需要另一对（S1和S2 - 3）。在这里，我们首次表明，成核特有的结构域（S4 - 6）或切断特有的结构域（S1）会竞争G - 肌动蛋白亚结构域1上的同一区域。我们进一步表明，在G缓冲液条件下，S2 - 3与肌动蛋白单体的结合较弱，并且当S1或S4 - 6也结合时，这种相互作用仍然存在。因此，凝溶胶蛋白与肌动蛋白上两个不同的区域相关联。由于S2 - 3在F缓冲液中不结合单体肌动蛋白，我们认为它与丝状亚基的1:1化学计量比的高亲和力反映了与两个相邻亚基的相互作用。
