학술논문
Gln49 and Ser174 Residues Play Critical Roles in Determining the Catalytic Efficiencies of Plant Glutamine Synthetase.
Document Type
Article
Source
Subject
*PLANT development
*ARABIDOPSIS
*CATALYSIS
*GLUTAMINE synthetase
*GROWTH of plant cells & tissues
*CYTOSOL
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Language
ISSN
0032-0781
Abstract
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 Km 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. [ABSTRACT FROM AUTHOR]