Dual role for the glutamine phosphoribosylpyrophosphate amidotransferase ammonia channel - Interdomain signaling and intermediate channeling

被引:43
作者
Bera, AK
Smith, JL
Zalkin, H [1 ]
机构
[1] Purdue Univ, Dept Biochem, W Lafayette, IN 47907 USA
[2] Purdue Univ, Dept Biol Sci, W Lafayette, IN 47907 USA
关键词
D O I
10.1074/jbc.275.11.7975
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Glutamine phosphoribosylpyrophosphate (PRPP) amidotransferase catalyzes the first reaction of de novo purine nucleotide synthesis in two steps at two sites. Glutamine is hydrolyzed to glutamate plus NH, at an N-terminal glutaminase site, and NH, is transferred through a 20-Angstrom hydrophobic channel to a distal PRPP site for synthesis of phosphoribosylamine. Binding of PRPP is required to activate the glutaminase site (termed interdomain signaling) to prevent the wasteful hydrolysis of glutamine in the absence of phosphoribosylamine synthesis. Mutations were constructed to analyze the function of the NH, channel. In time wild type enzyme, NH, derived from glutamine hydrolysis was transferred to the PRPP site, and little or none was released. Replacement of Leu-415 at the PRPP end of the channel with an alanine resulted in a leaky channel and release of NH, to the solvent. Mutations in five amino acids that line the channel and two other residues required for the reorganization of phosphoribosyltransferase domain "flexible loop" that leads to formation of the channel perturbed channel function as well as interdomain signaling. The data emphasize the role of the NH, channel in coupling interdomain signaling and NH, transfer.
引用
收藏
页码:7975 / 7979
页数:5
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