Gln49 and Ser174 residues play critical roles in determining the catalytic efficiencies of plant glutamine synthetase
Gln49 and Ser174 residues play critical roles in determining the catalytic efficiencies of plant glutamine synthetase
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DOI：
10.1093/pcp/pci238
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发表时间：
2006-02-01
影响因子：
4.9
通讯作者：
Takahashi, H
中科院分区：
文献类型：
--
作者：
Ishiyama, K;Inoue, E;Takahashi, H
通过对拟南芥谷氨酰胺合成酶（GS 1）的高亲和性（GLN 1;1和GLN 1;4）和低亲和性（GLN 1;2和GLN 1;3）同工酶的比对，确定了在决定GS 1底物特异性方面起关键作用的两个必需残基，并通过定点突变证实了这一点。结果表明，K49 Q或A174 S突变都足以通过降低其K值来提高GLN 1;3的催化效率。铵的值。与此相反，取代Gln 49和Ser 174赖氨酸和丙氨酸，分别是有害的谷氨酰胺合成活性GLN 1;4。结果表明，Gln 49和Ser 174在高亲和力的GS 1同工酶是可互换的，在相应的位置上的低亲和力的变体的Lys 49和Ala 174。
Two essential residues playing critical roles in determining the substrate specificities of cytosolic glutamine synthetase (GS1) have been identified from the alignment of high-affinity (GLN1;1 and GLN1;4) and low-affinity (GLN1;2 and GLN1;3) GS1 isoenzymes in Arabidopsis, and confirmed by site-directed mutagenesis. The results indicated that either K49Q or A174S mutation is sufficient to increase the catalytic efficiencies of GLN1;3 by decreasing its K. values for ammonium. In contrast, replacement of Gln49 and Ser174 by lysine and alanine, respectively, was detrimental to glutamine synthetic activities in GLN1;4. The results suggested that Gln49 and Ser174 in the high-affinity GS1 isoenzymes are interchangeable with Lys49 and Ala174 in the low-affinity variants at the corresponding positions.