Dissecting the molecular mechanism of ion-solute cotransport: substrate specificity mutations in the putP gene affect the kinetics of proline transport.
Dissecting the molecular mechanism of ion-solute cotransport: substrate specificity mutations in the putP gene affect the kinetics of proline transport.
复制标题
剖析离子-溶质共转运的分子机制：putP 基因中的底物特异性突变影响脯氨酸转运的动力学。
DOI：
10.1007/bf01951554
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Maloy,S
中科院分区：
文献类型：
--
作者：
Myers,RS;Townsend,D;Maloy,S
改变 putP 基因离散区域中脯氨酸通透酶簇底物特异性的罕见突变，表明它们可能取代酶活性位点的氨基酸。如果putP底物特异性突变直接改变脯氨酸通透酶的活性位点，则突变体应该在脯氨酸转运动力学中表现出特定的缺陷。为了测试这一预测，我们检查了 ThreeputP 底物特异性突变体的动力学。一类突变使 Kmover 增加 120 倍，但仅使 Vmax 减少四倍。此类K突变体可能在底物识别方面存在特异性缺陷，从而鉴定出对于底物结合至关重要的氨基酸。另一类突变使Vmax降低80倍而不改变Km。Vmax突变体似乎改变底物易位速率而不影响底物结合位点。最后一类突变改变了脯氨酸转运的 Kman 和 Vmax。这些结果表明底物特异性突变改变了对 Na+/脯氨酸同向转运至关重要的氨基酸。
Rare mutations that alter the substrate specificity of proline permease cluster in discrete regions of theputPgene, suggesting that they may replace amino acids at the active site of the enzyme. IfputPsubstrate specificity mutations directly alter the active site of proline permease, the mutants should show specific defects in the kinetics of proline transport. In order to test this prediction, we examined the kinetics of threeputPsubstrate specificity mutants. One class of mutation increases theKmover 120-fold but only decreases theVmaxfourfold. SuchKmmutants may be specifically defective in substrate recognition, thus identifying an amino acid critical for substrate binding. Another class of mutation decreases theVmax80-fold without changing theKm.Vmaxmutants appear to alter the rate of substrate translocation without affecting the substrate binding site. The last class of mutation alters both theKmandVmaxof proline transport. These results indicate that substrate specificity mutations alter amino acids critical for Na+/proline symport.